Figure 5. — Plate of Salzblrg 

 Anaphoric Clock, a reconstruc- 

 tion (see footnote 14) based on 

 a pliotograpli of the remaining 

 fragment. {Courtesy of Oxford 

 University Press.) 



■^-~~. TV.;,, 



Parts of two such discs from anaphoric clocks 

 have been found, one at Salzburg '' and one at 

 Grand in the Vosges,'' both of them dating from 

 the 2nd century A. D. Fortunately there is sufficient 

 evidence to reconstruct the Salzburg disc and show- 

 that it must have been originally about 170 cm. in 

 diameter, a heavy .sheet of bronze to be turned by 

 the small power provided by a float, and a large 

 and impressive device when working (see fig. 5). 



" First publisiied by O. Benndorf, E. Weiss, and A. Rchm, 

 Jahreshejle des oslerreichischen archdologischen Instilut in Wicn, 

 1903, vol. 6, pp. 32-49. I have given further details of its 

 constiuclion in A history oj technology, ed. Singer, Holmyaid, 

 and flail, 1957, vol. 3, pp. 604-605. 



'^ L. Maxe-Werly, Mi-moires de la Sociite jVationale des Ari- 

 tiquaires de France, 1887, vol. 48, pp. 170-178. 



PAPER 6: CLOCKWORK, PERPETUAL MOTION DEV 

 471274—59 7 



Literary accounts of the anaphoric clock have been 

 analyzed by Drachmann ; there is no evidence of the 

 representation of planets moved cither by hand or 

 by automatic gearing, only in the important case 

 of the sun was such a feature included of necessity. 

 .\ model "sun" on a pin could be plugged in to any 

 one of 360 holes drilled in at equal intervals along 

 the band of the ecliptic. This pin could be moved 

 each day so that the anaphoric clock kept step with 

 the seasonal variation of the limes of sunrise and 

 sunset and the lengths of day and night. 



The anaphoric clock is not only the origin of the 

 astrolabe and of all later planetary models, it is also 

 the first clock dial, selling a standard for "clockwise" 

 rotation, and leaving its mark in the rotating dial 

 and stationary pointer found on the earliest time- 



ICES, AND THE COMPASS 



91 



