MOUNTAIN OBSERVATORIES IN AMERICA AND EUROPE. 3 



and therefore from "glare " about the sun. From Norway Bond pro- 

 ceeded directly to Switzerland, where the experiment was tried.* 



The 2 -foot reflector constructed by Lassell and mounted by him 

 near Liverpool was taken to Malta in 1852 chiefly for the purpose 

 of obtaining better views of the planets. The 4-foot reflector, also 

 constructed by Lassell in 1859, was mounted at Malta during 1861 

 and remained there until 1865. The change from England to Malta 

 was made in search of better astronomical conditions ; and it is note- 

 worthy that Lassell's first expedition (1852) antedated the Teneriffe 

 experiment by four years. Sir John Herschel's expedition to the Cape 

 of Grood Hope was not in search of better conditions but for the pur- 

 pose of making a survey of the southern sky. 



In the year 1856 Professor Piazzi- Smyth made his famous expedi- 

 tion to Teneriife, where he established telescopes of sufficient power at 

 two stations of altitudes of 8903 and 10,702 feet, respectively. The 

 whole question of good vision f was thoroughly studied during a two 

 months' stay. The effects of fogs, local clouds, wind, dust, moisture, 

 etc. were noted. The general conclusion was extremely in favor of 

 that particular mountain-station. 



The results of the expedition were printed in scientific journals and 

 also in a popular book which had a wide circulation. :{: There is no 

 doubt that this expedition served to attract general attention to the 

 matter of choosing suitable sites for observatories ; and also to spread 

 the idea that all mountain-stations possessed striking advantages. 



Lassell's expedition of 1852 was, however, the first practical recog- 

 nition of the fact that a large telescope can only do its work well under 

 conditions specially favorable. These conditions may be found on a 

 mountain, or (for some work) they may be found at sea-level, as at 

 Malta. If the necessity for a specially favorable site be once recognized, 

 the search for the proper conditions is a matter of detail. The credit 

 for a clear comprehension of the conditions necessary for a great tele- 

 scope we must give to Lassell. 



Captain Jacob, a keen-sighted observer, early recognized the advan- 

 tages of a good observing station. At the time of his death (1862) he 

 had procured a 9-inch refi'actor which he intended to mount in the 

 Nilgiri Hills (Southern India). 



A letter from Dr. Henry Draper to Professor George P. Bond 

 ' (dated November 21, 1864) suggests that the best place to establish a 



' * The AmeHcan Journal of Science, 3d series, vol. x, pp. 81-83, contains ac- 

 counts of this experiment extracted by the writer from Professor Bond's Ms. 

 diary, by permission of his daughters. 



t Good " seeing," as it is called in the United States — following a convenient 

 expression which we owe, I think, to the veteran observer, Alvaii Clark. 

 t Teneriffe — An Astronomer's Experiment. 



