Author: אבי גולן

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The clock of the doors and the Jewish question

Introduction

The clock of the doors is identical to the candle clock of the monkey in terms of its mechanism and does not warrant a separate post. Just like the old joke about “The Elephant and the Jewish Question,” the clock of the doors has nothing to do with Jews,  which are not mentioned in the “The Book of Knowledge of Ingenious Mechanical Devices” even once. The phrase “The Elephant and the Jewish Question” is usually used to describe an annoying person who tries to link any event, however universal, to the Jewish people and their problems. I hope I’m not one of them, and I don’t have any convincing reason why I went out to check what we know about the Jews of Diyarbakır and Anatolia in the 12th Century. However, what I discovered is strange and exciting, and maybe it will interest you too.

The Candle Clock of the Doors” The Book of Knowledge of Ingenious Mechanical Devices, “Topkapi manuscript, 1206

How does it work?

Al-Jazari himself wrote:

” It is like the previous model, from which nothing is omitted except the keeper and the monkey. The additions are as follows: around the perimeter of the candle holder, fourteen doors are erected, each with two leaves. When a constant hour has passed from the lighting of the wick, a ball falls from the falcon’s beak, and the door opposite the falcon opens, and a figure emerges, [made] according to the choice of the craftsman.”

Anyone interested in the mechanism can go back and read my explanation of the monkey clock or the candle clock of the scribe. I will briefly explain the opening of the doors.

During combustion, the candle will shorten, and the force exerted by the weight will push the candle mount upwards at a constant rate that depends on the rate of combustion. To the bottom of the weight is attached another wire that runs over the pulley on which the bracket sits with 14 doors. These rotate as the candle burns. When the ball falls, it pushes the figure who opens a door and represents the time that has passed. This process repeats itself every hour.

The Jews in the 12th Century

The history of the Jewish people in the 12th Century is not similar in Ashkenazi communities and Muslim Spain. In Europe, the 12th Century began with the Rhineland massacres, a series of mass murders of Jews perpetrated by mobs of the People’s Crusade in 1096. The communities on the Rhine (Speyer, Worms, and Mainz) were destroyed. In 1146, in a repeat of the events of 1096, Crusaders preparing for the Second Crusade attacked and massacred Jewish communities along the Rhine. The 12th Century more or less ended with One of the worst Jews massacres of the Middle Ages, which took place in York in 1190. An angry mob trapped the city’s entire Jewish community inside the tower of York Castle. Many members of the community chose to commit suicide rather than be murdered or forcibly baptized by the attackers.

In Spain, on the other hand, Jewish people under Muslim rule experienced tolerance and integration. Some historians refer to this period as the “Golden Age” for the Jews, as more opportunities became available to them. That lasted from the days of the Caliphate of Cordoba to the small independent Muslim principalities and kingdoms of the Iberian Peninsula known as “taifas” and the process of the reconquest of Spain by the Christians. Social integration allowed Jews to advance significantly in new fields, philosophy and science. Some of them wrote poetry, primarily Hebrew poetry. They wrote about everything: poems about Zion and the people of Israel, but also poems about wine and women. I don’t think there’s a connection between the cultural flourishing in Diyarbakır and the Jewish flourishing in Muslim Spain, but it’s still intriguing. The Golden Age began in the 9th Century and ended in the 13th Century, but some of the more familiar figures were almost parallel to al-Jazari. For example, Maimonides was born in Cordoba in 1138, two years after al-Jazari, and died in Cairo in 1204, two years before him. Maimonides is a true polymath: one of the most prolific and influential Torah scholars of all generations, as well as a prominent philosopher of the Middle Ages, a scientist, and a physician. In his thirst for wisdom, he formed a study group and a friendship with Jabir ibn Aflah (a Muslim scholar) ‘s son, and they studied mathematics, medicine, and philosophy together. This must sound strange to those who live in Israel today and are familiar with the ultra-Orthodox opposition to secular studies. The “Kuzari” book, ” Book of Refutation and Proof on Behalf of the Despised Religion,” which I still managed to study in high school, was written by Rabbi Yehuda Halevi in this Century, and I must mention Rabbi Abraham Ibn Ezra, a 12-century poet, linguist, biblical commentator, and philosopher. He also worked in mathematics and astronomy. One of the lunar craters is named after him. Ibn Ezra’s most important mathematical work is in Hebrew: “The Book of the Unit,” which deals extensively with the decimal system and how it is used, thus preceding Fibonacci, the main contributor to the spread of this method in the Western world.

Did al-Jazari know the books they wrote or even heard about them? It is impossible to know, but the likelihood is extremely low.

Jews in Diyarbakır

In 1518, the Ottoman government conducted a census. There were 28 Jewish families and three single men in Diyarbakır. These are the first definitive data we have. After that, a continuous Jewish presence peaked in 1905, but apparently, the presence of Jews in Anatolia predates the Muslim conquest. According to traditions held by the Jews of Kurdistan, the Jews arrived in Kurdistan as early as the Salomon’s Temple period and are descendants of the Ten Tribes. As written in the book of  Kings:

” In the ninth year of Hoshea, the king of Assyria took Samaria, and carried Israel away unto Assyria, and placed them in Halah, and in Habor, on the river of Gozan, and in the cities of the Medes.”

Although we do not have a complete geographical identification, the name “Habur” has been preserved to this day as one of the Tigris tributaries located near the city of Zaxo (Arabic: زاخو), about 300 km from Diyarbakir. Later exiles to Babylon by Nebuchadnezzar, King of Babylon from the Kingdom of Judah, joined them. So it is very likely that there were Jews in Diyarbakir in al-Jazari’s day.

A Jewish delegation meeting with an Ottoman official

The Strange Story of David Alroy

Alroy was born a year before al-Jazari in Amadiya, Kurdistan. At first, I was confused because the historical name of Diyarbakır is Amida, but these are two different cities. Amadiya is located in northern Iraq, about 400 km southeast of Diyarbakir. David Alroy studied rabbinical literature with Hasdai, the exilarch, the leader of the Jewish community in Persian Mesopotamia, and Ali Gaon, the head of the Sanhedrin,  an assembly of elders appointed to sit as a tribunal in Baghdad. There is a claim that he was also well-versed in all the Books of Magic and sorcerers. I’m not sure what books are included, but it’s a bit like Chekhov’s gun, which appears in the first act, firing in the third. I have already mentioned Benjamin of Tudela, and not for the better. He wrote:

” David Alroy took upon him to rebel against the King of Persia [in 1163] ; for which purpose he gathered together all the Jews on the Mountains of Haphton, and from other Nations, to go to lay Siege to Jerusalem A great Part therefore of the Jews had Faith in; him, calling, him their Messiah. As soon as the King of Persia heard of this Matter, he commanded him to be brought before him. The King asked him: “Are thou the King of the Jews?” He answered and said, “I am,” The King then called to his Guards, and commanded him immediately to be apprehended, and led away to prison in the City of Dabastan. Three Days after this, as the King was sitting together with his Princes and Chief Minitiers, deliberating about the Jew Rebellion, behold David, having made his Escape from prison and approached and stood before him. The King looked at him and enquired, “Who brought thee hither?” He answered: “My own wisdom, and my own Subtilty because I fear neither thee nor any of thy Servants.” At which the King cried out: “Seize him!” But his servants said: “We see him not, but only hear the sound of his voice.”

Alroy then crosses the river on his handkerchief, and the King’s servants are unable to catch him in their boats. The King threatened to kill all the Jews in his kingdom. The frightened Jewish community threatened Alroy with a total exclusion from the Jewish community (“HEREM”). “In the end, David Alroy was killed in his bed while sleeping.

The story has legendary elements (seeing and not being seen, walking on water) absent in the description of Alroy’s contemporary, Al-Samawʾal ibn Yaḥyā al-Maghribi, who converted to Islam. To me, comparing the stories is less important than the passage describing the Baghdad Jews’ yearning for redemption:

“In this letter [a letter that two men forged in the name of David Alroy], they announce to the Jews of Baghdad the coming of the redemption they have been waiting for generations, in which they determine the night when they will all fly to Jerusalem, the holy city. Although the Jews of Baghdad were proud of their wisdom and strength of mind, they nevertheless tended to believe in this thing. Their wives brought all their possessions and jewelry to these two men so that they could divide all the property as they saw fit. In this way, the Jews wasted all their possessions. They wore green clothes and gathered that night on the rooftops of the houses, eagerly awaiting the moment when they would fly on the angels’ wings straight to Jerusalem. The women raised their voices in tears because they feared that they themselves would fly first before their children or the babies they were breastfeeding, and then these babies would suffer hunger.”

It is pretty clear that the Crusades and the instability in Palestine and nearby countries resonated strongly with some Eastern Jews, who saw them as precursors of redemption. The fantastic picture of the preparations for the flight and the heartbreak of the morning after also appear in other sources. Was all this commotion the talk of the day in Diyarbakir? This time not in distant Cordoba but in neighboring Amadiya,? We don’t know; even if it did, it must have been a minor event in al-Jazari’s world.

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A Goblet which arbitrates during drinking parties

Introduction

It is a tall goblet made of silver. The goblet has a fretted, flat lid with a beautiful dome in the center. On top of the dome, there is a duck with an open beak. The goblet is put in the middle of the party, and wine is poured. The duck rotates and emits a shrill tone until it comes to rest and stops whistling; its beak is pointed towards one of the participants who drink from the spout and empties all the wine and returns it to the steward, If however, any wine remains in it the duck whistles and the steward would not accept the goblet until the chosen one completed the drinking.

A drawing of the Goblet which arbitrates, Topkapi Manuscript, 1206

How does it work?

The technical explanation will be colored in blue as always, so anyone who is not interested in how a pitcher of wine makes sounds and how you know how much wine was drank can skip those bits. The drawing below is by the book translator and annotator, Donald R.Hill. It would help us to follow the mechanism:

The goblet mechanism following the drawing by Donald Hill.

The servant pours the wine on the fretted lid. The wine flows downward through the opening on the water wheel. Please see below the beautiful drawing by al-Jazari, which looks just like a modern turbine of NASA. The flow of wine hits the blades and rotates the wheel and the duck, which is on the axle. The wine goes down into the channel into the goblet, driving the air from through the air pipe and the whistle. When the drinker drinks from the spout, the wine goes back in the opposite direction, but if the drinker did not finish the wine, it will come back and push air in the pipe, and the duck will make a sound indicating that the drinker did not complete his duty.

A comparison of the water Wheel by al-Jazari and a modern turbine, NASA website.

 

Alcohol?

I am not an expert on Islam and its development, but the casual reference to alcohol drinking surprised me very much. I’ve explored the issue a little bit, but I would love to receive your corrections, comments, or other proposals. The prohibition on alcohol in the holy Quran is gradual. Muslims believe that Allah did so in his great wisdom and understanding of human nature and the knowledge of how rooted is alcohol consumption. In the beginning, Muslims were prohibited from participating in prayers when drunk:

Surah An-Nisa [4:43]:

“O you who have attained to faith! Do not attempt to pray while you are in a

state of drunkenness, [but wait] until you know what you are saying”

Further, it is said that alcohol is more damage than good:

Surah al-Baqarah 2:219:

“They will ask thee about intoxicants and games of chance. Say: “In both there is great evil as well as some benefit for man; but the evil which they cause is greater than the benefit which they bring.”

And only, at last, there is a sweeping prohibition:

Surah Al-Maida, 5:90

“O you who have attained to faith! Intoxicants, and games of chance, and idolatrous practices, and the divining of the future are but a loathsome evil of Satan’s doing: shun it, then, so that you might attain to a happy state!

All English translation by Muhammad Asad.

Despite the prohibition on drinking wine and intoxicating beverages in Islam, you can find many testimonies for drinking alcohol in the medieval Islamic world in language, culture, and poetry.  The word “alcohol” itself comes from the Arabic word al-kuhul (الْكُحْل) means the essence. This is because the production process is reminiscent of the production of the Kahal powder used as a dark eye-coloring cosmetic. In poetry, Abu Nuwas, probably the most famous Arab poet of the Abbasid era who also appears in “Thousand Nights and Nights,” wrote wine poems, The Khamriyyāt. You can be read more here:

“Don’t cry for Layla, don’t rave about Hind!

But drink among roses a rose-red wine,

A drought that descends in the drinker’s throat,

bestowing its redness on eyes and cheeks.

The wine is a ruby, the glass is a pearl,

served by the hand of a slim-fingered girl,

Who serves you the wine from her hand, and wine

from her mouth — doubly drunk, for sure, will you be!”

The Story of Bayad and Riyad, 13th-century Manuscript, Vatican library

“The drawing is from the manuscript “The Story of Bayad and Riyad”( حديث بياض ورياض).  This is the only manuscript left; it was probably created in Andalusia very close to 1200 (the years in which al-Jazari wrote “The Book of knowledge of Ingenious mechanical devices”) The scene in the picture is clearly a feast in which a group of women and men drink wine together.

The goblet which arbitrates is evidence that the court of Diyarbakir has lived with this contradiction in peace. There are plenty of references to Islam and its customs in the book, and there are playful fun drinking parties without any apology or concealment. We only have to guess the explanation. The Arctic rulers lived among a diverse local population, including Armenians, Syrians, and Greeks, most of them oriental Christians. In Christianity, not only wine is not forbidden, but it is a part of the ritual. At the Last Supper of Jesus, Jesus blesses the wine, states that the wine is his blood, and instructs the disciples to drink from it. Then he passed unleavened bread around the table and explained to his Apostles that the bread represents his body. These are the roots of the Holy Communion ceremony. It is possible that living together led to a softer approach to drinking wine. However, the evidence for alcohol use comes from all over the Muslim world from Persia to Andalusia and also spans for hundreds of years. I may be dumping the strict current prohibition on periods where the perception of early and late in the holy Quran was different and religious concepts were more moderate.

Truth or Dare?

My beloved M., the first reader of my posts, commented on the resemblance between the rotating duck and the bottle in the game “Truth or Dare”. This is a party game I last played as a teenager and was particularly popular among adolescents. The Internet offers application (few!), which make me feel that what was daring at my time is quite innocent today. On the other hand, it seems as though the game is still popular and therefore needs have not really changed?

Seemingly, this is a different game. The participants sit in a circle and spin a bottle. The participant to whom the bottle was pointed was asked: “Truth or Dare?” If you choose “truth”, you are asked a question that you must answer. At the time, all the questions were opened in: “Is it true that…” And most of them, if not all, dealt with things that are between him and her. If you choose “Dare”, you are given a task that opens with words “I dare you..” and most of those were the first kisses or something ridiculous. The question I think is why we need a bottle? Or in the context of the goblet which arbitrate why in duck?  Adolescents, at least in my time, were embarrassed about discovering their sexuality and the relationship with the opposite sex. The use of a game frame and temporary loss of control for the benefit of the “bottle” allowed expanding the boundaries and experimenting with what was difficult to ask or say without the protection of the game and could bring about embarrassment or reprimand. Does this mean that the partners at the banquet needed a duck that arbitrates because they felt discomfort with drinking alcohol? is this a question mark on my assumption that the goblet is clear evidence that the court of Diyarbakir lived with this contradiction in peace?

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The monkey’s candle clock and Falcons

Introduction

The monkey’s candle clock is very similar to the scribe candle clock and does not justify a post. However, the clock includes a Falcon. It made me go back and see what animals reside in Al-Jazari’s book. There are quite a few: an elephant, a lion, and a monkey. You can check how knowledgeable you are in the book if you know where the lion is hiding? (Unfortunately, there are no prizes for correct answers). There are some unidentified birds, a fish with no name, an ox or a donkey, al-Jazari gave no details, but used دابّة – daba which means an animal as well as two cows. On the more exotic side, there are five dragons (!) six peacocks (!!), and the champions of appearances in the book, to my great surprise, are seven Falcons. We have another perspective on Falcons and their special place in the Artuqid court from Usama ibn Munqidh(أسامةبنمنقذ), a medieval poet, writer, knight, and diplomat. I read his book “The Book of Contemplation” (in Hebrew, many thanks to Dr. Ella Almagor for her beautiful translation). There are numerous hunting stories, including falcons, at the court of the Emir Arslan, the father of Nur al-Din Muhammad, who hired al-Jazari. This will be the focus of this post.

Monkey’s Candle Clock Topkapi Manuscript, 1206

How does it work?

Al-Jazari wrote himself:

“The [following] are made as described previously: the candle-holder, the sheath, and the falcon; the two pulleys and the weight in the center of the interior of the sheath; the channel which covers the ball’s channel, inside which is the ball’s channel; the balls.”

Donald Hill, the book translator, and annotator, devoted to this chapter only a few lines, without a drawing, and wrote that the mechanism is the same as the scribe candle clock except for the vertical movement and not circular.  Still, I am briefly repeating the technical explanation, which as always, will be colored in blue, so anyone who is not interested in pulleys or balancing weight can skip those bits. The drawing below is by the book translator and annotator, Donald R. Hill [of the scribe candle clock] modified by me:

A drawing of the mechanism by Donald Hill with my modifications

The candle is placed on a holder inside a brass sheath, and only the wick protrudes through a hole in the cap. A long rod is soldered to the bottom of the holder. The rod runs through the main weight so that the weight is free to move up and down. Two strings are connected to the bottom of the rod and through two pulleys to the main weight. The latter is relatively heavy, slightly more than one kilogram. At nightfall, the wick is lit, at that time, the candle is in full size, the rod reaches its lowest point, and the main weight reaches its highest position. As the candle is consumed, the main weight will descend exerting force, through the pulleys, on the holder upward, and the holder and rod will go up at a constant rate, depending on the rate of the combustion.

To the bottom of the weight, another string is attached, through a pulley,  connected to the bottom of the rod on which the monkey sits. As the candle is consumed, the monkey will rise and point at the tick marks. There are 218 tick marks, and each represents 4 minutes and in total 14.5 hours Diyarbakir in the middle of the winter. The holder pulls the ball’s channel up, and every hour the highest ball in the channel has risen until it is level with the hole in the back of the falcon’s head, at which point it rolls out and falls from the falcon beak.

 

Usama ibn Munqidh

“The Book of Contemplation (كتابالاعتار, literally a  Book of learning by example) is an autobiographical book written by Usama ibn Munqidh, an Arab Syrian scholar and soldier of the 12th century, a son of the Munqidh, a noble Bedouin family that controlled the fortress in Shaizar in northern Syria.

Usama was a worrier and a hunter, but also a poet, a passionate book collector, and a diplomat with charm. He was born in 1095 in Shaizar, where he was educated and lived until 1131. When the men of the Shaizar did not fight the Crusaders or other opponents, they were hunting. Syria, in the 12th century, was heaven for hunters. I thought of rabbits, wild boars, and water birds, but to my surprise, there were also bears, lions, and tigers. The use of falcons and hawks was widespread. In 1162, when he fought alongside Nur ad-Din with the Crusaders of Antioch, he met Arslan, The Artuqid Emir. Upon the end of the battle, Arslan invited him to join him in the city of Hasankeyf, the home of the Artuqids, before they took over Diyarbakir. In the next decade, up to 1174, he spent hunting and writing in the Artuqid courtyard. The fourth section of his book is dedicated to hunting stories, and I’ll tell a little about what I learned about hunting with falcons and other birds of prey.

On Falcons and Falconry

Falconry is the art of using Falcons or the other birds of prey to hunt. Evidence suggests that falconry may have begun in Mesopotamia, with the earliest accounts dating to approximately 2,000 BC. Hunting with Falcons and hunting, in general, were a popular pastime in the period of the Umayyad and Abbasid Caliphates and were beloved also in the Artuqid Palace. Usama opens the hunting stories like this:

“I have in the above given those accounts of warfare and those experiences I had in battles, fights, and adventures which I could remember and which time with its rolling years did not make me forget. For my life has been prolonged, and I have for some time now been living in isolation and seclusion. Besides, oblivion is a heritage the antiquity of which goes back to our father, Adam (Peace be upon him!)  I shall now devote a chapter to what I have witnessed and partaken of in the field of hunting, be it the chase or falconry. Some of these experiences I had in Shaizar when I was still in the early part of life…and still others I had in Diyar-Bakr with al-Amir Fakhr al-Din Qara-Arslan ibn-Dawud  ibn-Urtuq (may Allah’s mercy rest upon his soul!).”

The great love for hunting is manifested through the story of his father, who was the ruler of Shaizar and gave up his throne:

“As for my hunting experiences in Shaizar, they were in the company of my father (may Allah’s mercy rest upon his soul!) Who was extremely fond of the chase, always talking about it and about collecting birds of prey, considering no amount of expense too great for the satisfaction of his curiosity in this sport…To him, the chase was in accordance with the following traditional saying: “Air ye your hearts so that they can better retain the word of Allah!” In fact, I never saw anything like his hunting and his ability to organize parties for it.”

An Arab-Syrian Gentleman and Warrior in the Period of the Crusades: Memoirs of Usama Ibn-Munqidh – Philip K. Hitti, 1929

The book is not a guide for the Falconer, but the stories contain a lot of practical information, for example, how did they hunt the falcons?

“All that was necessary was to have a stone house built to the height of a man. It would then be covered with branches concealed under hay and grass, with an opening. The trapper would then secure a pigeon, perch it on a stick, binding its two legs tightly to the stick, and display the pigeon from an opening, as a lure. As he moves the stick up and down, the pigeon flutters its wings. Seeing it, the falcon turns down and pounces on it to seize it. As soon as the hunter feels the falcon, he pulls the stick back to the opening, stretches out his hand, and seizes the two legs of the falcon.”

There are plenty of stories, but the story of al-Yahshur, an exceptional falcon demonstrates the unique relationship between the Muslim nobility and the predatory birds used for hunting:

Between Osama’s father and the sons of Rubal, the ruler of Armenia was a relation of friendship, and every year they would send him several falcons. One year a young broad like a saker [A falcon native of Southern Europe and Asia] arrived, but it could not keep up with the other falcons in flight, yet the falconer Ghana said, “Among all the falcons there is none like this young one, It will let no game escape it”. We could not at first believe him, but for the next thirteen years, al-Yahshur was the king of the hunting birds in Shaizar. The special relationship between his father and al-Yahshur can be seen here:

“When we entered the house, my father would say, “Fetch me a bowl of water.” They would fetch him one, and he would offer it to the falcon [al-Yahshur] while it was still on his wrist (may Allah’s mercy rest upon his soul!). The falcon would drink it. In case it wanted a bath, it would shake its beak in the water. My father would then order that a big basin full of water be brought and would offer it to the falcon… when it would get out of the water. My father would put it on a large wooden perch, especially made for it and would bring near it a brazier of live coal; and after it was combed and rubbed with oil” until it was dry, a folded piece of fur would be placed by it. The falcon would go down to it and sleep. It would remain among us sleeping on the fur until late in the night, at which time my father would want to retire into the harem’s apartment. He would then say to one of us, “Carry the falcon.” And the falcon would be carried as it lay sleeping on the fur until it was placed near the bed of my father (may Allah’s mercy rest upon his soul!).”

My love, M. says that I cannot tell about hunting with birds of prey without refereeing my readers to the movie about Aisholpan:

A young Mongolian girl who hunts with a golden eagle. This is, before anything else, a story about the power of a young woman who has managed to change Mongolians traditions. However, this is also a story about the deep connection between the hunter and his hunting bird. This is why there is no surprise in the number of falcons that penetrated al-Jazari’s machines.

A miniature of a falconer, North France, 1180.

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The Perpetual Flute, control, and knowledge sharing

Introduction

The Book of Knowledge of Ingenious Mechanical Devices contains four perpetual flutes. On the first one I wrote here, the current post is about the remaining three flutes. Each flute has a single page in the book, in comparison the Elephant Clock which takes twenty-two pages and the Castle Clock who is the champion with forty-one pages! The flutes are much simpler and are based on a single principle of compressing air in water containers to creates the sound. The name “flute” is somewhat misleading, and a whistle might be more appropriate as no fingering or an ability to change the pitch(sound frequency).  Some alteration is achieved through the use of two flutes (two whistles), each with a different sound. The uniqueness of each perpetual flute is the way al-Jazari control switching between the two flutes, and this is the main focus of this post.

Three perpetual flutes, left of the tilting buckets, center balance and on the right floats. Topkapi manuscript, 1206.

Fine technology and control theory

A considerable part of the work of al-Jazari falls in the category of fine technology. The term “fine technology” historically, embraces a whole range of machines for various purposes: water clocks, automata, astronomical instruments (not al-Jazari), and more. Some were intended to measure time or for other scientific needs, some for fun and amusement. What was common to all these devices, is a considerable engineering skill and subtle use of mechanisms and control systems. Control theory deals with dynamic systems (change over time) and how their behavior depends on feedback. This is a very wide field with applications from biology to robotics. The control theory contains heavy mathematics that scares students at the Technion and dates from the 19th century ~ seven hundred years after al-Jazari.

Despite mathematics, the control questions remain identical from the 12th century to the present day. It’s easy to think about air conditioning. When We define the desired temperature, the air conditioner will continue to cool as long as the room is above the set temperature and stop its operation when the room is at the right temperature. Although it sounds simple, the control of the air conditioner requires differential equations, and it is relatively complex. Al-Jazari had no electronics or detectors, but the same exact task. There is no difference between activating and stopping the air conditioner and activating and stopping the “perpetual flute.” The four perpetual flutes are a comprehensive class, with demonstrations, in the possible control methods for a 12th-century engineer.

How does it work?

The technical explanation, as always, will be colored in blue, so anyone who is not interested in tilting pipes and floats can skip those bits. The three flutes are identical in all their components except the control system. All three of the perpetual flutes have a permanent water supply. In all cases, there are two water tanks to which two flutes, or more precisely whistles, are attached. All the water tank are being emptied using a siphon. There’s an explanation of a siphon here. It almost seems like al-Jazari has prepared a lesson on control systems, so he made sure that all other elements are identical. In all three flutes, the water flows into a bowl welded to a pipe or a tilting apparatus. The pipe is slightly heavier on the right side, and the water flows towards tank B and fills it. The air that was in the tank is compressed out through flute B, which makes a whistling sound. When the tank is full, the control system will transfer the flow of water to tank A, and the siphon will empty tank B. This process repeats itself as long as the water flows.

  1. Perpetual Flute with tipping buckets. We have met the tipping buckets several times, for example, in “The fountain that changes its shape” or “The automaton of a standing slave holding a Fish and A Goblet”. The tipping bucket (in red) is balanced, as you see in the drawing. When it is full, according to the sketch it will happen at any minute, the weight of the water at the front-end is heavy enough to make the tipping bucket swing, and the rod (marked) will push the bowl upward so it would tilt to the left and water would fill the other tank
  2. Perpetual flute with balance controlThe tilting pipe has two openings. The main opening fills Tank, A as can be seen in the drawing below. The secondary opening is smaller, and the water flows diagonally to the balance pan. This is a classical scale, and the weight of water in a bowl will pull the tilting pipe in its direction. When Tank B would be full, the weight of the water would be enough to turn the tilting pipe to start filling tank A.  to fill the container in. Pay attention to the dish attached to the bowl and make it empty its waters.

  1. Perpetual flute with buoys

Each of the tanks has a buoy chamber. When the water rises in the buoy rises with them, and the rod attached to it will cause the tilting pipe to reverse the direction of the flow of water, and the water flows toward the other tank.

Generosity of Knowledge

At the end of the book, al-Jazari writes:

“In this five chapters [a little strange, there are six categories in the book, I have not seen anyone who discussed this discrepancy?] I have described roots which have many branches and great usefulness. When the descriptions are mastered, from them many more [things] may be created. I have omitted to mention many devices which I invented, for fear of obscurity or ambiguity. In what I have mentioned there is information for him who seeks information and profit for him who has zeal.”

I think that al-Jazari wrote these lines personally to me. Al-Jazari’s address bore fruits. The book in general, and these chapters specifically are written for a future reader who would like to learn and build the machines.

  1. Al-Jazari was ahead of his time in his willingness to share knowledge. The Cathedral of Vasily the Blessed is one of the most famous monuments in Moscow. It was built in the sixteen century on orders from Ivan the Terrible. The architect was probably Postnik Yakovlev. According to the legend, Ivan the Terrible blinded Yakovlev so that he could never build anything so beautiful again. It is unclear whether the legend is true, or just a myth, but the desire to preserve knowledge, or ability, is familiar to all of us from the workplace or the university or at least from the literature and movies. Al-Jazari is the opposite. He really went out into the world with a passion to share his knowledge. In this way, he is a magician of engineering, who broke the oath of magicians and brought the hidden knowledge to all mankind.
  2. The world as a whole assumes that “knowledge is money.” It can be seen in the payment we charge for consulting, in the patents industry and more. There is a secondary alternative stream in which people and companies are willing to share free knowledge for their enjoyment and joy of sharing. The open-source movement, the makers, centers in the community or Wikipedia are just a few examples. How to maintain this, what is the model of existence is a complex question that did not bother al-Jazari, an engineer in Saleh Nasser al-Din’s Artuqid Court.
  3. I do not know about the attempts of building machines from the book in seven hundred years since his writing, but quite many attempts to realize al-Jazari’s vision in the 20th century and the 21st centuries. You can read about restorations here. In all cases, the mechanisms, the machines worked wonderfully. I am building the elephant clock from Legos [Hebrew] these days and hope that I will continue this tradition.

 

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Two additional basins for bloodletting and what can we know about al-Jazari’s education?

Introduction

Al-Jazari described four basins for measuring the amount of blood during bloodletting. I already covered two of them: The basin of the monk was explained here with some background on the history of bloodletting, and I explained The Basin of the Two Scribes here with a discussion on the uniqueness of al-Jazari in comparison to other tools for bloodletting. The remaining two: The Basin of the  Reckoner (الحسيب -alhasib) and the Basin of the Castle are almost identical in their mechanism to those explained. The main difference is how the cumulative amount of blood is displayed. This made my mind wander further, and this time what can we know about al-Jazari ‘s education?

The Basin of the Reckoner, dispersed manuscript, 1315, the Museum of Fine Art, Boston.

What do we know about al-Jazari’s education?

We don’t know anything about al-Jazari’s education apart from what he himself wrote in the introduction:

“I have studied the books of the earlier [scholars] and the works of the later [craftsmen] –masters of ingenious devices with movements like pneumatic [movements], and water machines for the constant and solar hours, and the transfer by bodies of bodies from their natural positions. I have contemplated in isolation and in company the implications of proofs. I considered the treatment of this craft for a period of time and I progressed, by practicing it, from the stage of book learning to that of witnessing, and I have taken the view on this matter of some of the ancients and those more recent [scholars]. I was fervently attached to the pursuit of this subtle science and persisted in the endeavor to arrive at the truth. The eyes of opinion looked to me distinguish myself in this beloved science. Types of [machines] of great importance came to my notice, offering possibilities for types of marvelous control”

Beyond these lines, we have no information about his education or teachers. However, he was an avid reader who read quite a bit. I wrote about the library of al-Jazari here. His mathematical knowledge, at least according to the book, is limited. I wrote about it here. He is a diverse craftsman in a way that is almost impossible today; he was designing in metal, wood, and paper pulp. He worked with a large number of metals: iron, bronze, copper, brass, silver, and gold. He worked in a wide range of techniques: soldering, casting and hammering and produced himself pipes and gears. In fact, other than the raw materials, he does everything himself. The Makers movement, which is an umbrella term for independent inventors, designers, and tinkerers who preferred to be makers instead of consumers, could use al-Jazari as a role model.

What do we know about medieval education?

From the 8th century AD, elementary schools became generally adopted between the ages of six and ten. The classes were sometimes held in a shop or private houses, but more often in a mosque or building connected to it. The base for learning was the Quran. The pupil copied a passage of the  Quran on his board, and only after he had memorized it, moved to the next passage. We should remember that Muslims believe that the Quran was orally revealed by God to the final Prophet, Muhammad, and not only the Quran is the basis of the religion of Islam, but also a guideline for worship, the book of laws and an instruction book for the proper behavior. It was relatively common to see a procession in honor a ten years old child as a reward for studying the entire Quran by heart.

In addition to the Quran, the students learned the Five Pillars of Islam, including the ritual washing and the prayer. The non-religious teaching elements included verses of poetry as a model for writing and something about numbers and calculations. The schools were intended for all, and initially, no payment was collected for religious reasons. Over the years, it has changed, and the schools have received gifts, food, and money. At the end of the Umayyad Caliphate ((اَلْخِلافَةُ ٱلأُمَوِيَّة‎ in the 9th century, there is evidence of a school that contained 3000 pupils, it is clear that such an organization cannot operate without resources. Al-Jazari likely studied at this kind of school.

When the student completed the four compulsory years, he could go on for another three more years in which he studied grammar, rhetoric, and literature as well as the history of Islam. There are no references to literature or history in Al-Jazari’s book, and it is difficult to know if he continued his studies beyond the first four years. I didn’t find a medieval painting, but the contemporary photograph of Muslim pupils who are memorizing the Quran is probably quite similar to the 12th century:

Muslim students study the Quran in the mosque in India

After the four years of compulsory education, most of the students worked with their parents in the fields or were sent to work with a master craftsman as an apprentice. The work as an apprentice was conducted in small workshops of the bazaars(بازار). The bazaar is a network of narrow streets,  wide enough for a loaded donkey to pass through, usually covered with a wooden roof or some shaded areas, in which the workshops simultaneously created and sold their merchandise. The workshops were organized by guilds. Bernard Lewis, the historian who specialized in oriental studies, wrote the most authoritative work on Muslim guilds. He claimed that “guilds are one of the most interesting and characteristic phenomena of medieval Muslim civilization.” They are not merely equivalent of the European guilds, but so important was the guild in Muslim life, that in many cases the very topography of the Muslim city was determined by the needs of the guilds. From Morocco to Java, with surprising uniformity, the Muslim town rose around three or four central points, always the same. The first fixed point is the exchange. Around it is the toll-gatherer, the local mint (where there is one), the auction market, and the Muhtasib, or inspector of markets. The second center is the Qaisaria, a strong, closed-in building where foreign goods and valuables are stored. The third is the thread-market (Suq al Ghazl), where the women come to sell their own handiwork. And here, too, are the commodities women are likely to buy- butchers, bakers, etc. The fourth center is the university, usually attached to a mosque. Around these four centers are distributed the guildsmen; each guild in its own market.

At the head of the guild is the Sheikh. He is elected by the master craftsmen. Once selected, he was the unchallenged ruler of the guild, combining the functions of CEO, Treasurer, responsible for the taxes for the authorities responsible for the festivities and the concern for the sick and the poor. After him in hierarchy came elders among the master craftsmen, and next come the master craftsmen, the main body of the guild and finally the apprentices. The rank of a journeyman, skilled workers that have completed official apprenticeship qualification but may not yet work as self-employed master craftsmen so essential to European guilds, almost did not exist.

The apprentice (Mubtadi – مبتدئ) was taught by the master’s decision, for an unspecified period of time and without a specific curriculum. Some sources mention 1001 days that sound more like a ceremonial period than a three-year training. As the Apprentice training began at age 11, it was unlikely that they become independent craftsman at the age of 14. In most cases, the apprentice had to demonstrate his ability by producing a particularly complex piece of art (in Lewis’s words “masterpiece”), and then the master decided that the apprentice period was completed. The apprentice did not usually get paid during the apprenticeship, but the master did take care of their needs. Al-Jazari, unfortunately, does not write anything about this period of his life. I am pretty sure he went apprenticeship, and I would be very interested to know how was the experience.

It is impossible to talk about vocational education in Israel without entering a minefield. For many years, the youth of Edot HaMizrach (descendants of Jewish communities in the Middle East and North Africa ) were sent to vocational education( welding, metalworking, or barbershop training) regardless of their qualification. Only a highly detached consultant could send the deceased Ronit Matalon [an Israeli writer], with her amazing Hebrew to vocational education, and there are certainly many more examples.

However, the combination of vocational schools and apprentice training has many advantages. Germany, Switzerland, Denmark, as well as other countries have been demonstrating for years how vocational education can produce master craftsman that can not be replaced. I went to a traditional high school, and from there to the university and never, not even in Santa Clara or Portland, I didn’t feel that my education was short in comparison to the finest engineers in the world. Even so,  sometimes I want to go back and be the apprentice of al-Jazari and learn by doing and watching the very best.

 

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The Candle Clock of the Swordsman

Introduction

Candle clock is an ancient device for measuring the passage of time. The earliest reference is a Chinese poem by You Jiangu (AD 520). It appears in Wikipedia and other places, but I couldn’t find the poem itself, any help would be appreciated. These were simple clocks that were based on the relatively stable burning rate of candles. Linear graduation specified the elapsed time. All four candle clocks by al-Jazari are complex, full of inventions, a daring leap comparing to the classical candle clocks. In the clock of the Swordsman, the falcon emits a bronze ball every hour, so that the number of accumulated balls indicates the number of hours passed from sunset, at the same time the swordsman swings his sword and clips the top of the wick.

The Swordman Candle Clock, a Manuscript from 1315 Syria.

How does it work?

Al-Jazari opens the chapter of the candle clock of the swordsman with these words:

“I say that I have never come across a work by anyone on candle-clocks and have never seen a completed [example of such a] clock. I heard tell, however, of a candle-holder with a brass candlestick on it in which was a wax candle whose wick went through a hole in a cross-piece at the top of the brass candlestick. Near the foot of the candlestick was the head of a lion. When a constant hour had passed from the lighting of the candle, a ball fell from the mouth of the lion.”

The clock al-Jazari built was his version to the clock in the tale. The technical explanation, as always, will be colored in blue, so anyone who is not interested in balancing weights or bayonet mounts can skip those bits.

On the right side, the swordsman clock, Topkapi manuscript, 1206, with my explanatory captions. On the left is a three-dimensional sketch of the same clock based on the drawing by Donald Hill.

The massive candle, a height of about 40 centimeters (a span- شِبْر and a half) and almost four centimeters in diameter is standing on a cast bronze base. On the base, there is a brass sheath. The sheath is not a perfect circle but has two “lips” forming the ball channel, containing fourteen bronze balls. The candle alone blocks the balls. A heavy balancing weight of ~ 1.2 kg is connected through a pulley system. The weight guarantees that the bronze base and the candle are being pushed upward all the time. The length of the candle prevents the base from rising. The burning rate of the candle is measured meticulously, and the height of the candle is calculated so that it is suitable for sixteen hours of combustion, in practice, it would only burn for fourteen hours.

When the candle is lit at nightfall, the fire melts the wax, and after one hour the candle is shorter by 1/16. The weight will go down by this amount, and the base would go up, and the candle does not block any longer the lower ball. The ball is released and falls into the pouch attached to the string which is connected to the extension of the hand of the slave. As a result, the slave strikes the wick with his sword and cuts off the burnt-away section. The ball then rolls down and goes into the falcon’s head and then falls into the pedestal of the candle-holder. This happens at every hour until the end of the night

The part of the black slave and his sword is less detailed in my opinion, and its construction will require more experimentation and adjustments. Al-Jazari himself warns the reader that ” This movement [was perfected] after arranging and calculating and [after] repeated trials.”

Al-Jazari worked in the 12th century almost six centuries before Joseph Priestley discovered Oxygen, wax chemistry was also unknown at his time, and so was the understanding of Capillary Action. Despite this, his strong understanding of various materials, from working and experimenting, brings him to a few insights that we can now explain with the science we have learned. For example, al-Jazari requested that the candle will be made of pure wax. Candles can be prepared from natural fat, beeswax, whale fat, oil derivatives, and more. The rate of combustion depends on the combustion material, and as the material is more uniform, the rate of the combustion will be more uniform. He determines the weight of the wick, six grams. The wax is rising in the wick by capillary action, and therefore, various wicks will have different burning rate and would alter the time measurement.

One last thing, quite insignificant for the clock but interesting never the less. The candle cover was designed to replace candles comfortably. This method of mechanical attachment is known as “Bayonet mount,” and despite its exotic name, it is a useful technique of attachment  to this day, for example in camera lenses or electric lights and includes a cylindrical male side with one or more radial pins, and a female receptor with matching L-shaped slots and with spring(s) to keep the two parts locked together:

The source of the peculiar name is the use of soldiers in this type of connection to quickly attach bayonets at the ends of their rifles, but the first documented bayonet mount is undoubtedly al-Jazari book in this chapter.

My chemistry teacher and Michael Faraday

In 1972, I was sixteen and studied in the Tichon Hadash in Tel-Aviv. It was the only year we studied chemistry. To my shame, I do not remember the name of my teacher, even though one of her classes is engraved in my memory as an extraordinary experience that affected me deeply. We were the second class to start our high school in the seventh grade before there were middle schools in Israel, we went through screening exams, and we were smart, at least in our own eyes and smugly knowledgeable. When the teacher said:  “We would learn today about the candle.” The class broke into laughter; it seemed childish and not “scientific” enough for us. I’m afraid I’ve been among the laughing. Pretty soon she asked why the wax was burning up the wick and not burning in the candle? At once, in a fraction of a second, as in a revelation, I understood three things:

  • First, that despite my laugher, I do not understand the candle burning at all.
  • Secondly, there is a fascinating science in the most trivial things around us, like candles I have known well from Chanukah ceremonies and Shabbat candles.
  • Third, I don’t ask questions, which If I were the young man I hope to be, I would ask.

That’s a lot for a single lesson. My chemistry teacher knew nothing about the internal storm  I went through, and after years when I became a teacher myself, I thought about this lesson and I was hoping that sometimes I get to my students even when I don’t necessarily know about it.

When I worked at the Davidson Institute, Dr. Oved Kedem, my friend, introduced me to a thin book:

Six lectures on “The Chemical History of a Candle” that Michael Faraday gave at the Royal Institute in London in 1848 as part of the tradition of Christmas lectures for young people.

Michael Faraday was an English scientist, one of the best experimentalists in the history of science with an unusual life story. He was born into a poor family in London and was forced to help support the family as an apprentice in a local bookbinder and bookseller shop at age fourteen. He acquired all his education by reading books that were in the shop. The beginning of his scientific career was in popular lectures by Sir Humphry Davy, the president of the Royal Society at the time, so that his Christmas lectures were closing a circle. You can find the original book here. Those who do not want to deal with the original text can watch the series of short films done by Bill Hammack to present and explain Michael Faraday’s lectures.

On the fourth page, Michael Faraday answers the question  of my chemistry teacher:

 “Then there is another point about these candles which will answer a question—that is, as to the way in which this fluid gets out of the cup, up the wick, and into the place of combustion. You know that the flames on these burning wicks in candles made of beeswax, stearin, or spermaceti, do not run down to the wax or other matter, and melt it all away, but keep to their own right place. They are fenced off from the fluid below, and do not encroach on the cup at the sides. I cannot imagine a more beautiful example than the condition of adjustment under which a candle makes one part subserve to the other to the very end of its action. A combustible thing like that, burning away gradually, never being intruded upon by the flame, is a very beautiful sight, especially when you come to learn what a vigorous thing flame is—what power it has of destroying the wax itself when it gets hold of it, and of disturbing its proper form if it come only too near.”

This booklet is a real gem, and I met it much more experienced, after completing three degrees in science, but I was still fascinated and surprised by the opening sentence  that opened the lectures, and I think that al-Jazari would be curious too:

“There is not a law under which any part of this universe is governed which does not come into play and is touched upon in these phenomena. There is no better, there is no more open door by which you can enter into the study of natural philosophy than by considering the physical phenomena of a candle.”

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The peacock which discharges water from its beak and peacocks as a symbol

אַז די פאַווע קוקט אויף אירע פֿעדערן – קוועלטזי, אָבער אַז זי קוקט אויף אירע דאַרע פֿיס- וויינט זי”

“When the peacock is looking at its feathers she (in Yiddish peacock is always feminine) is happy and when she looks at her scrawny legs she cries”)

Introduction

The Peacock who discharges water from its beak to perform the ritual ablution is the sixth Peacock that we encounter in al-Jazari’s book; four peacocks in the water clock of the peacocks and another one in the basin of the peacock (in Hebrew). It’s time to talk about peacocks and many thanks to Dr. Shoey Raz that his comment sent me to this journey.

The peacock which discharges water from its beak. Topkapi manuscript, 1206.

How does it work?

The technical explanation, as always, will be colored in blue, so anyone who is not interested in siphons can skip those bits. The hollow peacock is quite similar to in the Basin of the peacock, which was already explained. It is made from copper large enough to contain the water needed for the ablution washing. Its curved neck is a siphon. A siphon is a tube in an inverted “U” shape, which causes a liquid to flow upward, above the surface of a reservoir, with no pump, but powered by the pull of gravity. I wrote more on siphons here. The peacock is a water container, hollow as far as the beginning of its neck. The tail is divided halfway up by a plate, so that the upper half of the tail forms a separate chamber, while the lower half is connected to the main reservoir. Al-Jazari made a secret plug with an extension which reaches to the top of the peacock’s tail. A siphon would only work when the water in the peacock reservoir reaches the bend of the siphon. Water is poured into the belly of the peacock until it rises to a point beneath the curve.  To start the ritual ablutions, a servant puts it down on a handsome pedestal in front of the king, rotates the valve slightly, the valve opens, and the water from the upper chamber flows into the peacock’s belly, and water flows through the siphon into the peacock’s beak and the ablution ceremony begins.

The peacock as a symbol

The Peacock is a native Indian subcontinent and serves as the national bird, but he has a long history in the Middle East. The Greeks discovered the Peacock following the conquest of Alexander the Great. However, they still managed to insert it into the Greek myths:

In one of his attempts to hide his infidelities, Zeus turned his lover, a water nymph named Io to a beautiful white Heifer. Personally, I find it a little insulting although Hera connection to the cow symbol is ancient and has to do with being the goddess of motherhood and fertility. Hera, who suspected (rightfully so!) the Zeus is chasing other women again, begged Zeus to give her the heifer as a present, which, having no reason to refuse, he did. Hera then sent Argus, a giant who had 100 eyes, to watch Io and prevent Zeus from visiting her. Argus’s eyes turned him into the ideal guard – while some slept, others were awake and open. Zeus sent Hermes to distract and eventually slay Argus and Hera transferred all his eyes to the tail of a peacock to thank and honor her loyal servant. The importance of Peacock in legends and myths is understood. The green, deep blue colors, won him the admiration and awe. The “eyes” on the tail were seen as a sign of comprehensive vision and wisdom.

I heard of the Yazidis only because of the horrible genocide by ISIS, but they have an exciting and unusual religion. According to their creation story, God was originally “over the seas,” a notion reminiscent of the Biblical passage: “And the Spirit of God moved upon the face of the waters.” playing with a white pearl. The pearl was broken and became the substance from which the Earth and other planets were formed. Then God created Tawûsê Melek (in Kurdish: طاووس ملك) translated to English as Peacock Angel with six other angles known as ‘the Seven Mysteries.’ All seven are part of God and not separated from him, fragments of God’s light, like Rainbow colors, are the light refractions. Tawûsê Melek is associated with the blue color while at the same time is the source of all other colors/angels. When Tawûsê Melek came to earth, the Peacock was(is?) the physical embodiment of the Rainbow. You can read more on the Yazidi religion and the Peacock Angel here [in Hebrew].

In Islam, there is more than one perception of the peacock. Some claim that the beauty of the peacock tail is a proof of Allah capability to create beauty to satisfy men passion for grace, and they rely on the Quran, Surah 35:27:

“Do you not see that Allah sent down water from the sky with which We brought forth fruits of diverse hues? In the mountains, there are white and red, of diverse hues, and pitchy black; and human beings too, and beasts, and cattle? Diverse are their hues. From among His servants, it is only those who know that fear Allah.”

It’s amusing to know that Charles Darwin, the father of evolution, was confused by the beauty of the peacock tail and thought (in error) that this contradicts or at least not support his theory of evolution. In a letter to Asa Gray, an American botanist, he wrote:

“The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick.”

In the Hadith Bihar al-Anwar, a comprehensive collection of traditions compiled by Shia Muslim scholar Mohammad-Baqer Majlesi I found this beautiful tale:

“Glory be to Allah, the King, the Holy. Glory be to Allah, the Great, the Most High. There is no god except Allah, the Living and Self Subsisting. ” Whenever the Angel would say this tasbih [repetitive utterances of short sentences in the praise and glorification of Allah] all the peacocks that are on the Earth would start to praise Allah and open their wings up in respect (of Allah). Whenever this Angel in the heaven would become quiet, the peacocks on the Earth would become quiet. The Angel in the heaven had green hair and white wings, so white that no one has ever seen anything that white before.”

There is also this sermon from Imam Ali, the cousin, and son-in-law of Muhammad, the last prophet of Sunni Islam and the first rightful successor to Muhammad by Shia Muslims which is strangely similar to the Yiddish motto:

“The peacock walks with vanity and pride, and throws open its tail and wings and laughs admiring the handsomeness of its dress and the hues of its necklace of gems. But when it casts its glance at its legs, it cries loudly with a voice which indicates its call for help and displays its true grief, because its legs are thin like the legs of Indo-Persian cross-bred cocks.”

There’s additional material about the Peacock in Islam and other cultures, but I can’t conclude this section without writing that peacocks from India appear already in the Bible:

“For the king’s ships went to Tarshish with the servants of Huram: every three years once came the ships of Tarshish bringing gold, and silver, ivory, and apes, and peacocks.” (KJV Chronicles II, Chapter 9, verse 21)

In Hebrew, the text is “Tukii” which in Modern Hebrew means Parrot. However, most translators and commentators believe that the original meaning was peacocks mainly because, in Tamil, the language spoken in Southeast India, Peacock is named Tukii.

A mosaic from the old synagogue Maon, the 6th-century ad

Did al-Jazari know the Greek mythology story about Io and Hera?  I doubt that very much. Did he know the stories about the Peacock from the Muslim tradition? More likely, but we will never know. Maybe he just liked peacocks? We have only our imagination, and all answers are right.

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The only measurement tool in the book and why al-Jazari is the first engineer

Introduction

Al-Jazari tells that when he mentioned to some people that any(not colinear) three points could be position on the circle they didn’t believe him, so he built the only measurement instrument in the book to find the center-point of three points of unknown position. The device is quite straight forward, but we can learn quite a bit from his choice to solve, what is clearly a mathematical problem, with an “engineering” solution.

An Instrument for finding the center of a circle, Topkapi, 1206

How does it work?

The technical explanation is so short that I decided to make an exception and not color it in blue. I hope you can forgive me. Al-Jazari took a ruler and built a vertical on the center point. He placed his instrument between the two points; found the center point and drew a perpendicular segment. He repeated the process for two more points. The intersection of the perpendicular segments is the center of the circle and the distance to each point is the radius. Besides, similarly to angle measuring instruments, there is an ark, which allows to measure and mark different angles.

Some Math

One can prove that any three points that are not colinear (al-Jazari was aware of this point and specify it explicitly) are on a circle in two approaches:

  • Euclidean geometry
  • Analytic geometry.

In Euclidean geometry, three points which are not colinear form the vertices of a triangle. All triangles can be within a circle. The center of the circle is the intersection of the three perpendicular bisectors. It is relatively easy to prove. If you want to practice your Euclidean geometry, look at the diagram below, build the three radiuses BO AO CO and prove they are identical using triangle congruence theorems. Euclid’s “Elements” was translated into Arabic relatively early in the House of Wisdom in Baghdad (بيت الحكمة )). There is no direct reference in al-Jazari’s book to Euclid, but his device is based on this theorems:

Right side drawing from my Euclidean geometry book, on the left a drawing by al-Jazari.

In a different approach, you can find the center circle with analytic geometry:

Circle equation, Analytic geometry

When:

r is the circle radius

a,b are the coordinates of the center point

Since the triangle has three vertices, we have three equations in three unknowns (a, b, r) and an immediate solution. Analytic geometry has roots in ancient Greece and Persia of the 11th century, but the breakthrough was made by René Descartes, philosopher, scientist and mathematician. We remember Descartes mostly because of the proposition “I think, therefore I am.” Descartes was a remarkable mathematician and the first to offer a system of axes (x, y), as in the diagram above, which is named after him: Cartesian coordinate system. It allows the graphical representation of functions. Generations of mathematics students were, are and will be very grateful. Also, he took advantage of the Cartesian system to connect geometry and algebra, creating analytical geometry. Descartes was an impressive polymath, his contributions to philosophy and mathematics are the pillars of the two disciplines, but he also was a key figure in the Scientific Revolution and made a contribution to optics.

Polymath and al-Jazari, the first engineer

A polymath (Greek: πολυμαθής) literally “having learned much” is an individual whose knowledge spans a significant number of subjects. Both in English and Hebrew we often use the term “Renaissance man” although all the “engineers” before al-Jazari were actually polymath long before the Renaissance:

Archimedes was a gifted mathematician, scientist, and engineer, who invented the “Archimedes Screw” (a pump, still used to this day), he has improved the power and the accuracy of the Catapult, made a giant crane known as “Archimedes Claw” not to mention the myth (?) of burning the Roman fleet using mirrors. All this pales in comparison to his contributions to mathematics and physics. Archimedes anticipated modern calculus and analysis by applying concepts of infinitesimals, developed the concept of buoyant force in “On Floating Bodies” and gave the mathematical explanation to the lever.

Hero of Alexandria was an engineer, mathematician, and physicist.  Hero may have been either a Greek or a Hellenized Egyptian. It is almost certain that Hero taught at the famous Library of Alexandria because most of his writings appear as lecture notes. He is known for his research in hydrostatics, but I have already written about Hero concerning his book on automata, he also built the Aeolipile, the first steam engine. In mathematics, Hero described a method for iteratively computing the square root of a number, but his name is most closely associated with Hero’s formula for finding the area of a triangle from its side lengths.

The Banū Mūsā (“Sons of Moses”) were three 9th-century Persian scholars who lived and worked in Baghdad. The Banu Musa wrote almost 20 books, the majority of which are now lost. They are known for their Book of Ingenious Devices on automata and mechanical devices. I wrote about them in the context of the fountains, but in the context of a polymath, we can mention their contribution to mathematics, The most important work of theirs is the Book on the Measurement of Plane and Spherical Figures, a foundational work on geometry that was frequently quoted by both Islamic and European mathematicians.

Al-Jazari is not like that. His contribution to engineering is diverse. I mention already the automata and the use of the camshaft, the significant advances in candle clocks [Hebrew] including the invention of the bayonet connection, the thermal insulation, the double-action pump but he was not involved in science or math or other fields outside engineering.

The concept of the Renaissance man was coined by Leon Battista Alberti ” A man can do all things if he but wills them”, a manifestation of the deep humanism in the roots of the Renaissance. The basic premise is that the infinite human ability to evolve, and we must embrace all knowledge in our way to develop our abilities. The world has expanded so that it is just impossible. Thomas Young, an English polymath in early 19th century, regarded by many as the last man who “knew everything” was skilled in medicine, physics, Linguistics, harmony (music) and even accounting. The web site of the Israeli medical association includes thirty-two different major specialties and more, numerous subspecialties. It is not possible, even theoretically, to complete all medical specialties during one life, let alone in other areas.

We live in a more skeptical and concerned world. We ask our children, already at a young age, “What do you want to be when you grow up? We narrow the field in high school and ask the students to find majors area of study where they excel. We have institutions, counseling centers, and tests to help young people choose their profession. A physics student will get the necessary mathematical background but will not receive academic credit for courses in Assyrian or typography. In second degree studies, we reduce the field of study further, and in Ph.D., we focus on one question only. As a society, we look at people that change profession with concern, maybe as less stable who lack the ability to focus.

Following Donald Hill, The book translator, and annotator and somewhat because of my own training, I thought that using an instrument (instead of a formal proof) indicates a limited background in mathematics. This may be true. My Love M. commented that mathematical proofs are less approachable to most people and lack the magic of the instrument al-Jazari built. Al-Jazari was the first “pure engineer” not because of lack of mathematical background, or ability in math and science, but because of his passion for engineering and his ability to translate abstract and formal issues to instruments.

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The Musical Boat for a Drinking Party

Introduction

The Musical Boat is the fourth of ten automata (mechanical dolls) and vessels that were designed to amuse guests at drinking parties at the King Court in Diyarbakir. On the boat deck seat the king, his and weapon-bearer, a slave holding a jug and goblet, as if serving drinks. Below there is a group of boon-companions and four slave girls, a flute-player, a harpist and two tambourine-players. The King and his court are static, papier-mâché sculptures. The musicians are made from jointed copper, and their arm can move. Professor Noel Sharkey sees in the unique mechanism al-Jazari designed for the drummer the world’s first programmable robot. More on this topic, below.

The musical boat, Topkapi manuscript, 1206

How does the boat work?

The boat moves gently on the surface of the pool at the Palace. Once every half hour, without any external intervention, a performance begins; The flutist would play the flute, the drummer would beat the tambourine, and the harpist plucks the copper strings. Here is a short mute (unfortunately) video of a model of the musical boat. After approx. Fifty seconds you can see the mechanism in action.

 

The technical explanation, as always, will be colored in blue, so anyone who is not interested in tipping buckets or early camshafts can skip those bits. The diagram below is the original drawing of al-Jazari with my captions:

The slave girls (musicians) are sitting above a water reservoir. The tank empties slowly into the tipping bucket. When the tipping-bucket has filled, after about half an hour, it discharges its water onto the scoops wheel, turning the wheel on its axle. The pegs on the axle rotate as well moving the rods which are connected to the slave-girls’ hands, moving them up and down. This creates the motion of the harpist plucking or the drum beating. The harpist has a three peg system for one hand, and the other hand is operated by one peg only. The rods are an early version of a camshaft and convert the circular motion of the axle to the linear movement of the musicians’ hands. The spacing between them generates different patterns of drumming or harp music. The water flows down into the pipe which is connected to the air vessel, forcing air through the whistle. This is the source of the “flute” sound.

Qiyan – Musician slave girls

The drawings in the facsimile edition were not done by al-Jazari. Donald Hill, The book translator, and annotator, detailed eleven manuscripts all over the world. The earliest copy, now in Topkapi Library (MS 3472) was completed by Muhammad Ibn Yusuf Ibn Uthman alHisenkafi in April 1206 and is the source of a facsimile. When a scribe finished copying a manuscript, a task that lasted weeks or even months, he would add a colophon, brief statement containing information about the publication such as information about the scribe and the manuscript. This is how we know that this copy was completed in 1206, the year al-Jazari died. We can assume that this copy was prepared from the original book, and the drawings are quite similar to the original. This is interesting because of the affinity between the Clothing of the boon- companions and the slave girls. The boon companions and the girls are all wearing qaba, a robe with sleeves, at mid-calf –between the knee and ankle that has a diagonal fastening of one side over the other. The color scheme is also identical. This made me think of them as “male musicians” Although the text is very clear about slave girls

Qiyān (Arabic: قِيان‎, ) was a social class of slave women, trained as entertainers, which existed in the pre-modern Islamic world. Qiyān is often rendered in English as ‘singing slave girls,’ but this translation does not reflect the fact that qiyān were skilled entertainers whose training extended well beyond singing, including composing music and verse, reciting historical or literary anecdotes, calligraphy, or shadow-puppetry and more. Qiyān were important in performing and distributing the works of the composers of the period in the Palaces of Islam from the eighth to the thirteenth century. They received broad education from an early age, including science, philosophy, and art. Beyond being gifted poets, dancers, or musicians, they were supposed to be courtesan with high conversational skills. There’s quite a bit of information about Qiyan in Baghdad, the Abbasid capital. In these years Bagdad was a cosmopolitan city and the center of science, culture, and philosophy. The musical slaves came from different cultural backgrounds. We know of Qiyān from all over the world, from Rome to India. They were bought in for outrageous sums of money, but the slavery is somewhat confusing, and those released remained in palaces in the same role? You can’t compare the tiny principality of the Artuqid with the Abbasid caliphate in Baghdad, but the presence of the Qiyan in Diyarbakir is another indication of the cultural flourishing in line with the original architecture  [Hebrew] and the initiative to write the ” Book of Knowledge of Ingenious Mechanical Devices.”

Musical robot

The word ‘robot’ was first used by Czech writer Karel Čapek in his 1921 play R.U.R -Rossum’s Universal Robots. The word ‘robot’ itself was not new, and come from Slavic language robota, meaning servitude. Oxford dictionary definition, “a machine capable of complex operations automatically, especially with programmable computer” is problematic, if only because my car is capable of a complex series of actions automatically, it has a large number of programmable electronics, and it is not a robot by any definition. In literature and science fiction movies, we use “robot” for an android, a machine resembling a human being and able to replicate certain human movements and functions.

Čapek’s book was written in 1921, long before Ted Hoff invented the microprocessor. When we talk about ancient robots and the automata al-Jazari built and ask ourselves if they should be considered as the predecessors of robotics, the questions should be two:

  1. Was it possible to program? Or in other words, do they have the ability to do different actions by design?
  2. Do they have autonomy? The ability to decide what to do and how to do it?

The question of “what was the first device that could be programmed?” is more theoretical than practical, but the musical boat is a leading candidate. Professor Noel Sharkey of Sheffield University built a model of a single drummer from the musical boat to illustrate how it can be “programmed.”  Beneath the ‘drummer’ was a rotating shaft with pegs on it. As these pegs rotated they pull on a lever that raised the drummer’s arm and then it dropped to hit the drum. The placement of the pegs entirely controlled the rhythm and timing of the drum beats. The purpose of the model was to demonstrate that one can play different beats using different peg patterns by changing the peg locations and spacing.

Did al-Jazari actually “program” the musical boat? We will never know. He probably used this method during the design to get the rhythm he liked. Whether it was used or not, the musical boat shows the possibility of “programming.” The question of autonomy will have to wait eight centuries until engineers would have sensors and computerized systems.  For those who want to expand, I attach a short (about ten minutes) film from the history channel. It introduces the subject of Robotics and the contribution of al-Jazari and other ancient robots. For some reason, they turned al-Jazari into a Persian?

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The Drummers’ Clock and Musical Robots

Introduction

The Drummers Clock is a water clock and probably one of the first drum machines and musical robot ancestor. It features five mechanical drummers: two cymbal players, two drummers with a drum slung over their shoulders, and a drummer sitting in front of two kettle drums. Despite significant advances in robotics and AI- Artificial Intelligence, musical robots fall short compared to human musicians; their music lacks subtleties and is “mechanical.” The simplicity of the drum machine, in contrast to a robot violinist, helps to focus on the real issue. This post moves between explanations of the drummers’ clock and thoughts on the difficulties in creating a “musical” musical robot.

The Drummers’ Clock, a dispersed copy, 1315

How does it work?

This is a simple version of the Castle clock with fewer mechanisms to display the time, and those that remained are simpler. The large components: The water tank, float, and flow controller are identical to the Castle clock and the “Time cart” is very similar, a little like a cheap version of a mobile phone. Al-Jazari does not explain them again but refers the reader to the first chapter (the Castle clock). I also turn directly to musicians. Al-Jazari writes:

 “When an hour has passed the musicians (نوبة – nūbah, a musical genre found in the North African, it has its origins in Arabo-Andalusian music.) perform with a clamorous sound which is heard from afar.”

The technical explanation, as always, will be colored in blue, so anyone who is not interested in tipping buckets or scoops wheels can skip those bits. The diagram below is the original drawing of al-Jazari with my captions.

The water flows on the scoop wheel once an hour. This is a large clock, and every time about eight liters of water flows. It is turning the scoop wheel on its axle so that the pegs move the rod which is connected by a copper chain to the slave-girls’ hands. The pegs are an early version of a camshaft and convert circular motion to linear movement. The number of pegs and the intervals between them create different patterns of drumming. The copper strip goes through the hollow wooden body of the musician, and when pulled it goes up and later falls to hit the drum. The pegs are organized in a way that is characteristic of the work of al-Jazari, two adjacent pegs, and a third peg apart. The result is two relatively fast beats, and a third after a pause. There are also two trumpet players, but they are only “decor accessories.” The sound of trumpets is produced separately by the water pouring into an air vessel and compressing the air out through the pipe with a whistle.  Al-Jazari used this in many devices, including the Perpetual Flute.

Robotics and the student’s disappointment

Robotics is an enjoyable and sometimes exciting way to teach and learn science and technology. This is true for excellent students and students with difficulties in mathematics and science. Most of the students gladly take upon themselves robotics problems, research a topic, and build a robot using original thinking and their ideas. I taught robotics in different settings: in elementary school Gavrieli, in middle school Branco Weiss and at the Davidson Institute of science education. I found it a creative learning experience in all the years I taught. Beyond the programming tools, mechanical engineering, electronics, and sensors, it teaches children to confront and overcome obstacles, builds confidence and self-esteem, and gives inspiration to science and technology. As a part of the introduction, I would present a wide range of robots, including a robot that plays the violin:

In almost every class I taught, students (happy and enthusiastic) were complaining that the robot’s performance is “mechanical” or “robotic” as a weakness. Violin has a wealth of nuances in how the violinist produces the violin sound (Timbre). This results from many choices, such as which string to use, the pressure of the bow, the point of contact, the bowing speed, to use the whole bow or only partially. All these choices reflect the musical understanding of the violinist and will echo emotionally with the listener. The Musical robot in the movie is programmed so that it “knows” to play the notes, but it has no musical understanding at all. The concept of an artistic interpretation is foreign to him. The drum machine is much simpler in comparison to the violin and will facilitate the discussion.

Musical robots and music

The drummer’s choice includes “merely” the question of the drums selection and the beating template. In terms of the drum machine of al-Jazari, this is the arrangement of the pegs for each drum and possibly changing the length to affect the volume. Al-Jazari made these decisions during “programming” or the design phase, but we can easily think of a modern drumming robot with all the parameters free to change in real-time. This will allow changing hand techniques and evolving drum beat patterns but will not progress us even one step toward musical interpretation.

This is a nontrivial challenge for robot builders. Robots in science fiction literature and toward the end of the 20th century are machines that can replicate human action, especially when it is repetitive. When Karel Čapek coined the word “robot” in the play R.U.R (Rossum’s Universal Robots), the idea was to replace humans when the work was tedious, difficult, or even dangerous. Prominent examples are the welding robots in the automotive industry or the Police Bomb Disposal Robot. In recent years, there has been a shift in direction, and a lot of research has been done on Artificial Intelligence (AI). There are exceptional results in various fields, including robotics stock traders, diagnostic medical robots, and precise surgery robots. What was considered thirty years ago insurmountable, like software playing chess or go (a Japanese board game) is a reality. Chess software like Komodo can beat any human grandmaster. The contribution of AI to music (AIM- Artificial Intelligence Music) is more modest and limited, at this time, to conferences and academia, and no robot can be matched to a human musician. People are not jamming to concerts to listen to musical robots. AIM is a broad field and includes many topics, some of which are relatively simple to understand, Like:

  • Methods to produce music using musical robots
  • Storage of digital music

Some are more complex, but still approachable:

  • Symbolic representations of music – how to represent music beyond the note, including “human touch” and interaction between musicians.
  • Human-computer interaction-music – how can a computer respond to music, including jazz improvisation.

Some are borderline science fiction:

  • Cognition Computational music – the idea is to teach the computer what is needed for music playing or composition. Moreover, to treat this as a process and do the same learning that does a composer/performer.

As someone who likes robots and automatons, maybe like al-Jazari at his time, I’m surprised by the pleasure I get from reading about the difficulties of the AIM community and the human abilities which are so hard to imitate. Despite what I wrote, I would like you to see the film below: I don’t know how it was done and what part is human, and what part is AIM, but it is certainly fun to watch and listen to!