llic orifice left open for filling the wheel. The wheel will 

 then revolve of itself, drawn around by the water. 



Description of a syphon: Make up a tube of copper 

 or other metal, and bend it in the form of an .\nkus"a or 

 elephant hook, fill it with water and slop up both ends. 

 And then putting one end into a reservoir of water let the 

 other end remain suspended outside. Now uncork both 

 ends. The water of the reservoir will be wholly sucked up 

 and fall outside. 



Now attach to the rim of the before described self- 

 revolving wheel a number of water-pots, and place the 

 wheel and these pots like the water wheel so that the water 

 from the lower end of the lube flowing into them on one 

 side shall set the wheel in motion, impelled by the additional 

 weight of the pots thus filled. The water discharge from the 

 pots as they reach the bottom of the revolving wheel, should 

 be drawn ofl' into the reservoir before alluded to by means 

 of a water-course or pipe. 



The self-revolving machine [mentioned by Lalla, etc.] 

 which has a tube with its lower end open is a vulgar machine 

 on account of its being dependant, because that which mani- 

 fests an ingenious and not a rustic contrivance is said to be a 

 machine. 



And moreover inany self-revolving machines are to be 

 met with, but their motion is procured by a trick. They 

 are not connected with the subject under discussion. I 

 have been induced to mention the construction of these, 

 merely because they have been incntioned by former 

 astronomers. 



Siddhanta Siromani, xi, 50-57, L. Wilkinson's translation, 

 revised by Bapii deva S(h)astri, Calcutta, 1861. 



Before proceeding to an investigation of the content 

 of these texts it is of considerable importance to 

 establish dates for them, though there are many diffi- 

 culties in establishing any chronology for Hindu 

 astronomy. The Surya Siddhanta is known to date, in 

 its original form, from the early Middle Ages, ca. 500. 

 The section in question is however quite evidently an 

 interpolation from a later recension, most probably 

 that which established the complete text as it now 

 stands; it has been variously dated as ca. 1000 to ca. 

 11 50 A. D. The date of the Siddhanta Siromani is more 

 certain for we know it was written in about 1150 by 

 Bhaskara (born 1114). Thus both these passages 

 must have been written within a century of the great 

 clocktower made by Su Sung. The technical details 

 will lead us to suppose there is more than a temporal 

 connection. 



\Vc have already noted that the armillary spheres 

 and celestial globes described just before these extracts 

 are more similar in design to Chinese than to Ptole- 

 maic practice. The mention of mercury and of sand 

 as alternatives to water for the clock's fluid is another 



feature very prevalent in ( Chinese biu absent in the 

 Greek texts. Both texts seem conscious of the com- 

 plexity of these devices and there is a hint (it is lost 

 and revealed) that the story has been transmitted, 

 only half understood, from another age or culture. 

 It should al.so be noted that the mentions of cords and 

 strings rather than gears, and the use of spheres rather 

 ihan planispheres would suggest we are dealing with 

 devices similar to the earliest Greek models rather 

 than the later devices, or with the Chinese practice. 



A quite new and important note is injected by the 

 passage from the Bhaskara text. Obviously intrusive 

 in this astronoinical text we ha\e the description of 

 two '"perijetual motion wheels" together with a third, 

 castigated by the author, which helps its perpetuity 

 by letting water How from a reservoir by means of a 

 syphon and drop into pots around the circumference 

 of the wheel. These seem to be the basis also, in the 

 extract from the Surya Siddhanta, of the "wonder- 

 causing instrument"' to which mercury must be 

 applied. 



In the next sections wc sliall show that this idea of a 

 perpetual motion device occurs again in conjunction 

 with astronomical models in Islam and shortly after- 

 wards in medieval Europe. At each occurrence, as 

 here, there are echoes of other cultures. In addition 

 to those already mentioned we find the otherwise 

 mysterious "peacock, man and monkey,'" cited as 

 parts of the jackwork of astronomical clocks of Islam, 

 associated with the weight drive so essential to the 

 later horology in Europe. 



We ha\-e already seen that in classical times there 

 were already two different types of protoclocks; one. 

 which may be termed "nonmathematical," designed 

 only to give a visual aid in the conception of the 

 cosmos, the other, which may be termed "mathe- 

 matical'" in which stereographic projection or gearing 

 was employed to make the device a quantitative 

 rather than qualitative representation. These two 

 lines occur again in the Islamic culture area. 



Nonmathematical protoclocks which are scarcely 

 removed froin the classical forms a[)i)ear continuously 

 through the Byzantine era and in Islam as soon as it 

 recovered from the first shocks of its formation. 

 Procopius (died ca. 535) describes a monumental 

 water clock which was erected in Gaza ca. 500.'' It 

 contained impressi\e jackwork, such as a Medusa 



'" H. Diels Uber die von Prokop bcschriebcnc Kiinstuhr von 

 Gaza, .■ibhandlnngen, Akademif der Wissenschajtm, Berlin, Philos.- 

 Hist. Klasse, 1917, No. 7. 



96 



BULLETIN 218: CONTRIBUTIONS FROM THE MUSEUM OF FIISTOR\' .AND TECHNOLOGY 



