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 object glasses is a difficult art which, at that time, had been lost in England, and had never been attempted in America. Notwithstanding the inherent difficulty of the task, increased many fold by the lack of teachers, the father and son worked away undaunted. At last they produced a four-inch telescope so good that Mr. Clark asked permission to exhibit it to Professor Bond at Harvard Observatory. The exhibition was a failure, not from any defect in the glass, but because it was not suitably mounted. Mr. Clark found means of correcting the difficulty, but his merit remained unrecognized for many years. American observatories ordered their instruments from Germany, not dreaming that their wants could have been supplied by a master here at home. It was an English amateur astronomer, Rev. W. R. Dawes, who first appreciated the skill of the Clarks and brought them into notice. He found their glasses to be of remarkably fine quality, and began to give them orders. They made several telescopes for him, and as he was known to be an unusually good judge of telescopes, this attracted attention, and Mr. Clark obtained a tardy recognition in his own country. His first large order was for an eighteen and one-half inch glass for the University of Mississippi. This was three and one-half inches greater than the lens of the Harvard telescope, which had remained unsurpassed for twenty years. In spite of the skill of Mr. Clark, the order could not have been filled, but for his good fortune in obtaining glass discs of the requisite size and purity. The casting of optical glass is a delicate and difficult art, and there are but one or two firms in the world capable of producing discs of large size. After a long
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