46 The Microscope. 



atoiy wMch was well equipped for practical work, containing among 

 other instruments, a clock, a chronograph, and a refracting telescope 

 with nine inch objective. In 1870 he was appointed assistant in the 

 observatory of Harvard University, and in 1877, elected assistant 

 professor of astronomy for a term of five years, on the expiration of 

 which in 1882 he was re-elected. In 1886 he accepted the position 

 of professor of astronomy and ]:)hysics at Colby University in Water- 

 ville, Maine, which last position he now occupies. 



The special astronomical work of Professor Rogers while at the 

 Harvard Observatory, has been in obsei'ving the position and map- 

 ping out all the stars down to the 9th magnitude, in a certain nar- 

 row belt of 5 degrees located a little north of our zenith. This work 

 has been done under the auspices of the German Astronomical 

 Society, of which he is a member. Thirteen similar belts were 

 assigned by that society to different observatories throughout the 

 world; two of them to the United States; the one already refen-ed 

 to assigned to Harvard and the other to Albany, N. Y. 



The observations of Professor Rogers on this work 'extended 

 over a period of eleven years, and required fifteen years for their 

 reduction. Four volumes of his observations have already been 

 printed and two more are now in the* process of preparation. Though 

 he has severed his official connection with Harvard, he still retains 

 supervision of his unfinished work at the observatory. His last pub- 

 lication relating to astronomy was a " Catalogue of 130 Polar Stars 

 for Epoch of 1875.0." The mathematical problems in this paper were 

 worked out by his able assistant. Miss Anna Winlock, and it may be 

 mentioned in passing, that this is the first time a pm'ely mathemat- 

 ical paper has been published where the work was executed by a 

 woman ; Professor Rogers' connection therewith being limited to the 

 methods of discussion adopted, and to an examination of the numer- 

 ical results obtained. 



Interesting as even an outline sketch would be of many of the 

 intricate astronomical problems which have come within the scope of 

 Professor Rogers' observations, of still more interest to the working 

 microscopist are the practical results obtained by him, through years 

 of original research in the broad field of micrometry. 



In his early investigations with the transit instrument at Har- 

 vard, Professor Rogers found the micrometer spider webs too deli- 

 cate to be clearly defined with the best illumination possible, in the 

 character of observations he was then engaged in. He therefore 

 began a diligent hunt for a spider whose web was sufficiently coarse 

 to overcome the difficulty. This little incident, trivial as it seems, 



