Deborah Jean Warner Alvan Clark and Sons Artists in Optics

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Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. Clarks made the objectives for the largest refracting telescopes in the world; and the fifth of their efforts, their 40-inch lens at the Yerkes Observatory, has never been surpassed. Their optical work, which was recognized as unexcelled anywhere in the world, was the first significant American contribution to astronomical instrument making. American telescopes had been made before, but none compared to those of Euro pean manufacture; by the end of the 19th century, however, partly because of the example set by Alvan Clark Sons, several other Ameri cans were making fine astronomical instruments.