Baghdad’s House of Wisdom also produced a collection of all of the mechanical engineering devices known at that time. It’s certainly a collection from China, India, Persia and Greece, like the other scientific works. We aren’t sure if the pictures in “The Book of Tricks” (or “Book of Ingenious Devices”) show us common devices, or rare ones, or even just theoretical ones.
The book was compiled by three brothers who were a major force in Baghdad’s scholarly community for many years. Their father was from Khorasan, an area of western Persia that was at first only lightly Islamicized. He was some kind of robber on the Silk Road, but the governor of Khorasan befriended him and took his three sons Ahmed, Mohammed and Hasan into guardianship. They were given the finest Persian and Arabic education and are credited with writing twenty scholarly books, mostly now lost. Some of the books were written by only one of them, while others are credited generally to the brothers, the “Banu Musa.”
Kitab al-Hiyal, the book of mechanical tricks, may have survived due to its popularity and many copies. The devices are basically elaborate toys, not productive machinery, but they show the array of possibilities to automate with merely mechanical methods. While the book collects the mechanical tricks invented by the Greeks, some of them appear to have been improvements or original inventions by the Musa brothers.
They were interested in how physical forces could automate processes, often using air and water pressure. They described different kinds of valves: plug, float, tap, and conical (presumably the last was their invention). They explained how to automate a fountain so that it alternated in the jet’s shape and type.
Some basic mechanical devices make a first appearance, although in primitive form. There is a very simple crankshaft, although not complete in its design. One device has a simple worm-and-pinion gear. The Banu Musa describe, for the first time, the action of a clamshell bucket for reaching to the bottom of a lake or river and dredging mud or removing lost objects.
They have a few automated musical instruments. We’ve all seen the mechanism inside a music-box: a cylinder with pins to trigger different-toned bars in a tune as the cylinder turns. Their water-powered organ seems to have used this idea. It’s one of the few devices we still know today, in a time when so few things need mechanical “programming.” They also had a steam-powered automated flute.
Steam, the power of the future, was only noted in passing in the book. It’s used only for toys that build up pressure, then suddenly let off a whistle or blow something into the air, to surprise and amuse a rich man’s dinner guests.
The High Middle Ages in Europe was a time of rapid industrial invention and change. It’s hard to know how much influence this book had on Europe’s blue-collar inventors. It was certainly valuable for collecting and preserving the inventions of Greece and adding some from China. Later books on mechanical devices used the Banu Musa book as a first reference; eventually some of these drawings may have come into the hands of practical, ambitious men who wanted something more than toys.