50 MOUNTAIN OBSERVATORIES IN AMERICA AND EUROPE. 



Professor Burnham's Experiments on Mount Hamilton in 1879 



(August 17 to October 17). 



In 1874 I suggested to the Lick Trustees that Professor Burnham, 

 using his 6-inch Clark refractor, should test the sites proposed for 

 the Lick Observatory before any final selection was made. In 1875 

 Mr. Lick selected the summit of Mount Hamilton, after some prelimi- 

 nary tests had been made by Captain Floyd, President of the Lick 

 Trustees, Mr. Frazer, and others, with small telescopes. 



Professor Burnham's expedition of 1879 was very important in its 

 systematic examination of double-stars and in its comparison with the 

 conditions obtaining at Chicago. During the whole period of sixty 

 days Professor Burnham reports : First-class nights 42 ; medmm 7 ; 

 cloudy and foggy 11. His general conclusions may be quoted here, 

 although they are well known, because they have been confirmed by 

 our long experience. They are, in brief, that " there can be no doubt 

 that Mount Hamilton offers advantages superior to those found at any 

 point where a permanent observatory has been established [up to 1879]. 

 The remarkable steadiness of the air, and the continued succession of 

 nights of almost perfect definition are conditions . . . not to be 

 met with elsewhere." 



In 1881 Professor Burnham and myself made a stay at Mount 

 Hamilton, after a season of observation at Madison, Wisconsin, which 

 had not changed the opinion above quoted. It is interesting to re- 

 mark that the site chosen for the 40-inch Yerkes refractor of the 

 University of Chicago lies about midway between Chicago and Madi- 

 son. Unless the conditions at Lake Geneva, Wisconsin, are distinctly 

 better than those of the region near by, its selection as a site for the 

 largest of telescopes may turn out to have been an error of judgment. 



Dryness of the atmosi:)here : Meteorological observations taken at 

 Mount Hamilton during the years 1888 to 1896 will soon be printed in 

 a special volume of the Contributions from the Lick Observatory. An 

 inspection of such tables in detail will exhibit, better than any words, 

 the remarkable conditions which exist here during the most favorable 

 observing weather, May to November. 



A botanical survey of the mountain was made, at my request, by 

 Professor Greene of the University of California in 1893, and a sen- 

 tence from his rejDort* exhibits the integral, as it were, of many sepa- 

 rate conditions : 



. . . Mount Hamilton having been chosen as the site of the Lick Observa- 

 tory on account of its being a fair-weather mountain ... it must be interest- 



* Erythea, vol. i, No. 4, April, 1893, page 77. 



