feet long by twenty-five feet wide, with an ell of the same width and thirty 

 feet long.' 7 Under the workshop the Clarks had a long chamber dug for 

 testing optical systems. A fireproof safe, with telegraphic alarms con- 

 nected with Alvan Clark's bedroom, housed the valuable lenses at night; 

 the lenses actually rested on a railway car which ran in and out of the 

 safe. 48 



In the years before the Civil War the Clarks made and sold about a 

 dozen medium-size lenses; the largest, of 12 inches aperture, showed 

 Mimas, the innermost satellite of Saturn. 49 For many of these they also 

 provided equatorial mounts. Then in i860 the Clarks received an order 

 for a lens larger than any ever made. The i8Vo-inch for the University 

 of Mississippi was to have an aperture 3 1/2 inches larger than did the 

 Harvard and Pulkowa instruments. This was the first of the five times 

 that the Clarks would progressively surpass the world's record for existing 

 lens size. In 1873 they finished the 26-inch for the United States Naval 

 Observatory ; and twelve years later a similar telescope was erected at 

 the University of Virginia. In 1883 they finished the 30-inch lens for the 

 Russian Observatory at Pulkowa. The 36-inch lens for the Lick Ob- 

 servatory was sent to California in 1887. And the 40-inch objective, 

 mounted at the Yerkes Observatory in 1897, is still the largest lens 

 ever used. 



Alvan Clark formally introduced himself to the American scientific 

 community at the 1850 meeting of the American Association for the 

 Advancement of Science in New Haven. He was then elected to member- 

 ship and attended meetings until that body dissolved, temporarily, ten 

 years later. The 1856 meeting, held at Albany to celebrate the dedication 

 of the Dudley Observatory,- was the largest and most representative 

 scientific meeting held in America before the Civil War. 50 Here Alvan 

 Clark met Robert Hare, whose portrait he painted soon thereafter; he 

 very likely also met F. A. P. Barnard, the newly elected president of the 

 University of Mississippi, who four years later commissioned him to build 

 the world's largest telescope. At this meeting Alvan Clark read a paper 



47 An occasional correspondent of the Tribune, "Two Giant Telescopes," Boston 

 5 February [n.y.] (clipping in library of the Maria Mitchell Association). 



48 Boston Journal of Chemistry, vol. 7 (1872), p. 56. 



49 American Journal of Science, vol. 29 (i860), p. 449. 



50 W. H. Hale, "Early Years of the American Association," Popular Science 

 Monthly, vol. 49 (1896), p. 503. 



