It may be readily accepted that the use of toothed wheels to transmit power or turn it through an angle was widespread in all cultures several centuries before the beginning of our era. Certainly, in classical times they were already familiar to Archimedes (born 287 B.C.), 3 and in China actual examples of wheels and moulds for wheels dating from the 4th century B.C. have been preserved. 4 It might be remarked that these "machine" gear wheels are characterized by having a "round number" of teeth

Before proceeding to a discussion of the controversial evidence which may be used to bridge this gap between the first use of gears and the fully-developed mechanical clock we must examine the other side of this gap. Recent research on the history of early me chanical clocks has demonstrated certain peculiarities most relevant to our present argument. the european tradition If one is to establish a terminus ante quem for the appearance of the mechanical clock in Europe, it would appear that 1364

Now that we have seen the manner in which mechanized astronomical models developed in China, we can detect a similar line running from Hellenistic time, through India and Islam to the medieval Europe that inherited their learning. There are many differences, notably because of the especial development of that peculiar characteristic of the West, mathematical astronomy, conditioned by the almost accidental conflux of Babylonian arithmetical methods with those of Greek geometry. However, the lines

We have already noted, more or less briefly, several instances of the use of wheels "moving by themselves" or the use of a fluid for purposes other than as a motive power. Chronologically arranged, these are the Indian devices of ca. 1150 or a little earlier, as those of Riḍwān ca. 1200, that of the Alfonsine mercury clock, ca. 1272, and the French Bible illumination of ca. 1285. This strongly suggests a steady transmission from East to West, and on the basis of it, we now tentatively propose an

The elusive history of the magnetic compass has many points in common with that of the mechanical clock. Just as we have astronomical models from the earliest times, so we find knowledge of the loadstone and some of its properties. Then, parallel to the development of protoclocks in China throughout the middle ages, we have the evidence analyzed by Needham, showing the use of the magnet as a divinatory device and of the (nonmagnetic) south-pointing chariot, which has been confusedly allied to th