year a 12-inch equatorial refractor was purchased from the Clarks for 

 $6280. 22 ° The clockwork of this telescope was regulated by the spring 

 governor taken from the 12-inch formerly owned by Henry Draper, 

 before it was sent to the Lick Observatory (qq.v. ) . The observatory and 

 large refractor were seldom used. The tube has been scrapped and the 

 objective lost. (See fig. 25, p. 100.) 



The well-equipped astronomical observatory at the U.S. Naval 

 Academy at Annapolis was used primarily for instruction. 221 Their large 

 refractor was made by the Clarks in 1857. The 734-inch achromatic ob- 

 jective had a focal length of 9 feet 6 inches (f/15 was the focal ratio of 

 most Clark lenses) ; the German style equatorial mount was supported 

 on a cast iron pier; the driving clock was regulated by a Bond spring 

 governor. During the total solar eclipse of August 1869 — the first astro- 

 nomical occasion on which Clark instruments were extensively used — the 

 Naval Academy's telescope was taken to Des Moines, Iowa, and used 

 photographically by Dr. Edward Curtis of the Surgeon General's Of- 

 fice. 222 The Academy's observatory has since been closed, and the tele- 

 scope has disappeared. 



The Civil War occasioned a change in the direction of the U.S. Naval 

 Observatory — a change which brought new jobs to the Clarks. Mat- 

 thew F. Maury, a southerner as well as an oceanographer, resigned his 

 commission in 1861. His successor, James M. Gillis, improved the instru- 

 ments and promoted the astronomical work of the observatory. 



In 1862 the Clarks refigured the objectives of most of the Washington 

 instruments, always with decided improvement both in achromatism and 

 definition. To replace the stolen 3.9-inch objective of the Merz und Mah- 

 ler comet seeker, Gillis asked both the Clarks and Henry Fitz for bids; al- 

 though the Clarks charged 50 percent more, and required much more 

 time than did Fitz, they got the job. 223 This object glass turned out so 

 well the Clarks were asked to rework the 5.3-inch lens of the Ertel merid- 



220 F. S. Harlow, "The Observatory of the U.S. Military Academy at West Point," 

 Publications, Astronomical Society of the Pacific, vol. 3 (1891), pp. 273-274. 



221 Charles Andre and A. Angot, V astronomie pratique el les observatoires en Europe 

 et en Amerique. Pt. 3: Etats-Unis d'' Amerique (Paris 1877), p. 1 12. 



222 U.S. Naval Observatory Reports on Observations of the Total Eclipse of the Sun, 

 August 7, i86g, p. 124. 



223 Alvan Clark & Sons to James M. Gillis, 21 April 1862; Henry Fitz to James M. 

 Gillis, 18 April 1862 (letters in U.S. Naval Observatory Papers, National Archives, 

 Record Group 78). 



97 



