as well, the Clarks made experimental castings at a Cambridge glass- 

 works. 42 Although the British opticians and scientists had long been ex- 

 perimenting with optical glass, theirs was as irregular as the American 

 product. For these reasons, Alvan Clark made his first lenses from objec- 

 tives of old instruments. 43 Fortunately, his need for better glass coincided 

 with the midcentury political upheavals that caused George Bontemps, 

 who was privy to the technical secret of making fine optical glass, to emi- 

 grate from Paris and to join the Chance Bros, glassmaking company in 

 Birmingham, England. Soon thereafter Chance Bros, began supplying 

 the Clarks with optical discs. Around 1875 tne Clarks turned to the house 

 of Feil-Mantois in Paris for their glass. All the large objectives figured by 

 the Clarks were made possible only by the successful castings of these two 

 factories. 



Optical blanks were as expensive as they were difficult to obtain. A 

 duty of 30 percent was levied on the purchase price, rather than the actual 

 value, of each imported blank. As these blanks often turned out to be opti- 

 cally worthless, and as they seem to have been nonreturnable, the duty 

 soon became oppressive. Clark finally brought suit against the customs 

 collector; he won the case, but in this minor Bleak House the damages 

 paid only the court costs. 44 In later years the Clarks were able to avoid 

 the duty when the glass was destined for a school, for the U.S. Govern- 

 ment, or — as in the case of the 30-inch discs for the Russian observatory 

 at Pulkowa — when imported by a foreign minister. 45 



In i860, after the order for the i8y2-inch lens had been received (see 

 below), the Clarks moved from Prospect Street to larger premises by 

 the Charles River (see fig. 12, p. 41 ). On an acre and a half on Henry 

 Street, near the Brookline Bridge, they built their workshop, an observa- 

 tory, and separate dwellings for the Alvan Clarks, the George Clarks, and 

 the Alvan Graham Clarks. Their location could be spotted from afar by 

 the tall telescope tube and mount which was used to test new objectives. 

 The outside grounds were covered with grass- and beds of flowers. 46 The 

 factory itself was an unpretentious two-story brick structure, about forty 



42 Charles Plumb to E. Mathews, 3 June 1879 (letter in Lick Observatory 

 Archives). 



43 Alvan Clark autobiography, op. cit., p. 113. 



44 Ibid., p. 114. See also Simon Newcomb, "The Story of a Telescope," op. cit., 

 p. 46. 



45 "Clark's Telescope Works," The Cambridge Chronicle, 2 January 1892. 



46 "The Alvan Clark Establishment," Scientific American, vol. 57 (1887), p. 198. 



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