the important contributions made by his two sons. There are several 

 obvious explanations for this. Through a common contraction Alvan 

 Clark & Sons became Alvan Clark. Before turning to astronomical 

 instruments, Alvan Clark was noted for his work in other fields; George 

 Bassett and Alvan Graham, on the other hand, devoted their entire 

 professional careers to Alvan Clark & Sons. Another reason is that toward 

 the end of his life Alvan Clark wrote a frequently reprinted and often 

 quoted autobiography; but his sons were more modest. Although each 

 had his own specialty — Alvan and Alvan Graham did optical work while 

 George did mechanical work- — it is impossible, in almost all instances, to 

 identify the man most responsible for a particular job. All three Clarks 

 should be remembered equally for the achievements of Alvan Clark & 

 Sons. 



No discussion of Alvan Clark & Sons would be complete without a list 

 of the instruments made in their shop. Previous articles on the Clarks 

 have emphasized, usually to the exclusion of all else, their objectives over 

 i8*/£> inches in diameter. These were indeed great achievements. The 

 Clarks, however, should also be remembered as very prolific craftsmen 

 who made a wide variety of astronomical instruments, including equa- 

 torial refractors, spectroscopes, chronographs, and micrometers. 



The second half of this volume is a descriptive catalog of instruments 

 made and remade by the Clarks between the dinner bell experiment of 

 1844 and the death of Alvan Graham Clark in 1897. 



