Introduction 



Three instrument makers — Alvan Clark and his sons, George Bassett 

 and Alvan Graham — figured importantly in the great expansion of 

 astronomical facilities which occurred during the second half of the i gth 

 century. Almost every American observatory built during this period, and 

 some observatories abroad, housed an equatorial refracting telescope, 

 and often auxiliary apparatus as well, made by the Clarks. Five times the 

 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. 



Fortunately, the Clarks lived at a time when men could afford as well 

 as appreciate their work. Astronomy had caught the public imagination 

 and the private purse. Astronomers, it was thought, could penetrate far 

 into space, discover new worlds, and evidence the glory of God. Equally 

 important, telescopes were obvious symbols of their donor's opulence; 

 these well-publicized monuments were seldom compared qualitatively, 

 but were always described by their size. Thus, when rich Americans 

 wanted to express their love for learning, and also wanted to insure their 

 fond remembrance, they often endowed telescopes and observatories. 



Many historical accounts discuss the work of Alvan Clark but neglect 



