

r,..»>^^^>^ 



Figure 12.— Gearing from Astrolabe Shown- in Figure ii. The gear train count is as 

 follows: 48-13 + 8-64 + 64-64+10-60. The pinion of 8 has been incorrectly replaced by a 

 more modern pinion of 10. The gear of 48 should make 13 (lunar) rotations while the double 

 gear of 64 + 64 makes 6 revolutions of double months (of 29-30 days) and the gear of 60 makes 

 a single turn in the hegiral >ear of 354 da\ s. (Photo cowU^y of Scieme Miiscum, London.) 



Tliis landmark in the history of science and tcch- 

 nolos\- is now preserved at the Museum of tiie 

 History of Science, Oxford, England.-' It is an asiro- 



2' I acknowkdgo with thanks to the Curator of that museum 

 the permission to reproduce photographs of this instrununt. It 

 is item 5 in R. T. Gunthcr, Astrolabes of the world, O.xford, 1932. 



labc, dated 1 22 1-22 and signed by the maker, Muham- 

 mad b. Abl Bakr (died 1231-32) of Isfahan, Persia (see 

 figs. 1 1 and 12 1. The very close resemlMance to the 

 design of Biruni is quite apparent, though the gearing 

 has been simplified very cle\crl\- so that only one 

 wheel has an odd number of teeth (13), the rest being 



PAPER 6: CLOCKWORK, PERPETUAL MOTION DEVICES, AND THE COMP.\SS 



99 



•JT1274— 59- 



