The first recorded job the Clarks did for Harvard was early in 1857; 

 they made a glass prism and were paid $ioo. 107 Many years later the 

 Clarks were involved in another Harvard prism incident. J. Trowbridge, 

 while a green, young instructor at Harvard, borrowed two valuable 

 prisms from the observatory and succeeded in chipping them; Joseph 

 Winlock, the director, replied only, "Oh, I always intended to get Alvan 

 Clark to reduce the size of these prisms, and he would have had to chip 

 off these edges." 108 



Later that year the Clarks played a key role in the first successful stellar 

 photography. The photographic experiments, made by George Bond 

 and John Whipple in 1 850, had been hindered as much by the irregular- 

 ity of the Munich clock drive as by the slowness of the daguerreotype 

 process. In a letter to the Royal Astronomical Society, seven years later, 

 Bond attributed their success to the collodion process, and to the new 

 spring-governor controlled clock drive "which has been adapted to the 

 great telescope by those excellent mechanicians, Messrs. George Clark 

 and Alvan Clark, jun., of East Cambridge, assisted by their father, Mr. 

 Alvan Clark, sen." 109 The first photograph, taken on 27 April 1857, 

 showed Mizar, its fourth-magnitude companion, and Alcor; the distances 

 between the images of these stars were measured the next day by Alvan 

 Clark with a reading microscope. 110 Inspired by Bond's success, at least 

 two notable astronomers — Dawes and Rutherfurd (qq.v.) — were led to 

 order equatorial mounts with spring-governors from the Clarks. 



Joseph Winlock became director of the Harvard observatory in 1 866 

 and began immediately to improve and increase the equipment. In 1 869 

 the Clarks completed the West Equatorial, a refractor of 5 J/4, inches 

 aperture, and 7 1 / 2 feet focal length, equipped with divided circles, spring- 

 governor driving clock, and spectroscope. The spectroscope, similar to 

 that made for Charles Young at Dartmouth (q.v.), consisted of five 

 prisms of dense Munich glass through which the light passed twice. 111 



107 Harvard College Papers, vol. 24, 2nd ser. (1857), p. 119. 



108 Quoted in J. Trowbridge, "Scientific Cambridge," in A. Gilman (ed.), The 

 Cambridge of Eighteen Hundred and Ninety Six (Cambridge, Mass., 1896), p. 76. 



109 "Letter From Mr. Bond, Director of the Observatory, Cambridge, U.S., to 

 the Secretary," Monthly Notices, Royal Astronomical Society, vol. 17 (1856-1857), pp. 

 230-232. 



110 Ibid. 



111 Annals, Harvard College Observatory, vol. 8 (1877), p. 35. 



66 



