The book describes in detail fifty devices (/ashkal/), which are groupedinto six categories (/anwa`/):1) ten water and candle clocks;2) ten vessels and figures suited for drinking sessions;3) ten pitchers and basins for phlebotomy and washing before prayers;4) ten fountains that change their shape alternately, and machines forthe perpetual flute;5) five water raising machines;6) five miscellaneous devices.Each device or /shakl/ is described in simple Arabic that is easy to understand, and each is accompanied by a general drawing. There are fifty of these and are numbered by the letters of the Arabic alphabet from one to fifty. For the complicated devices al-Jazari gave detaileddrawings for the components of a device or for subassemblies so that the operation could be understood. The edited version of his book based on the surviving manuscripts, contains a total of 174 drawings. An alphabet letter marks each part in a device. The text explains the construction of the device with the aid of the letters so that the reader canunderstand the device by reading the text and referring to the illustrations.
