Figure 17.— French Geared Astrolabe of Trefoil Gothic Design, en. A. D. 131",. Un- 

 gearing on the pointer is, from the center: (32)/i4-45+27-39. the last meshing with a concave 

 annular gear of 180 teeth around the rim of the rete of the astrolabe. A second pomter, 

 geared to this so as to follow the Moon, seems to be lacking. {Photo courtesy 0/ Science Museum. 

 London.) 



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BULLETIN 218: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



