SCIENCE. 



FKIDAY, SEPTEMBER 4, 1885. 



THE FUTURE OF THE LICK OBSER- 

 VA TOR Y. 



The history and description of this obser- 

 vatory, and the astronomical work ah-eady ac- 

 complished on Mount Hamilton, which we have 

 given on a later page, lead ver}' naturally to a 

 statement of the chief advantages which, in 

 so far as the observatory and its position and 

 equipment are concerned, may reasonably be 

 expected to accrue from this new departure in 

 astronomical science. 



The fact of mere elevation (less than a mile) 

 above the sea-level will not, as is often sup- 

 posed, greatly increase the apparent light of 

 celestial objects, as the stars will appear to be 

 only a small fraction of a magnitude brighter on 

 the mountain than at the sea- level. But — what 

 is incomparabh' more important — the gain in 

 steadiness of the atmosphere at this elevated 

 station has alread}^ been proven to be much 

 greater than an}' one expected at the outset, 

 and will enable the astronomer not only to 

 make good use of a multitude of clear nights 

 which, at less elevated stations, are found to 

 be of little value, but also to elevate the grade 

 of all his work to the last degree of precision. 

 The perfection of this site for observations 

 with the meridian circle — in fact, for all mi- 

 crometric observation of whatever sort — will 

 force the invention of better methods of elimi- 

 nating personal and instrumental errors than 

 we now possess. So far as the conditions of 

 vision affect the stars' diurnal motion, the 

 errors introduced in stellar co-ordinates will be 

 so small that two or three observations of 

 a star will suffice for the most accurate deter- 

 mination of its position. An enormous saving 

 in the labor of observation and reduction is 

 thus possible, if only the other errors can be 

 eliminated with certaint}' from so small a 

 number of observations. With regard to the 

 influence of elevation upon the conditions of 

 da3'-vision, it should be noted here that the 

 testimony of Mr. Burnham in 1879, of Profes- 

 sor Holden in 1881, and of Professor Todd in 

 1882, is uniformly to the effect that the atmos- 

 phere above Mount Hamilton is quite as un- 

 steady daring the daytime as at other stations. 

 This remai-k, however, must be understood as 

 applying onl}' to the period of the 3'ear from the 



No. 135. — 1885. 



middle of August to the middle of December, 

 as no accurate observations upon this matter 

 have been made in other months. It is ver}' 

 possible that the conditions of the atmosphere 

 in late spring and early summer may give an 

 entirely diff'erent experience at these seasons. 



The elcA-ation above a mile of the lower at- 

 mosphere becomes significant in another way, 

 however, as it makes effectively available a 

 much larger region of sky than can be com- 

 manded at other stations in a like latitude, 

 where observations at zenith distances much 

 greater than sevent}^ degrees are usuall}" not 

 worth the making. Mr. Burnham directs at- 

 tention to this fact, as affecting observations 

 in that portion of the southern celestial hem- 

 isphere which is ordinarily inaccessible for 

 observations of precision at our northern 

 observatories. At the latitude of Mount 

 Hamilton, the fifty- third parallel of south 

 declination is about co-incident with the south 

 horizon ; and, out of forty-two new double- 

 stars discovered by Mr. Burnham during his 

 residence upon the mountain in 1879, twenty 

 are between the thirtieth and fortieth parallels 

 of south declination (that is, between limits 

 of maximum altitude equal to twenty-three 

 and thirteen degrees) ; and five of the new 

 stars are between the fortieth and forty-fourth 

 parallels, or between limits of maximum al- 

 titude equal to thirteen and nine degrees onl3\ 

 This important advantage will not be confined 

 to the southern horizon only, but will dulj' in- 

 fluence all fields of astronomical inquiry where 

 important observations have occasionally' to be 

 taken near other parts of the horizon. 



The prevalence of violent winds on the 

 summit, and particularly their effect upon 

 the steadiness of the atmosphere, have not yet 

 been thoroughly investigated. As a general 

 rule, astronomers at ordinar}' elevations expect 

 to find severe winds accompanied b\' atmos- 

 pheric conditions which do not admit of satis- 

 factory micrometric work. Mr. Burnham 

 found that moderatelj" strong winds did not 

 seem to affect the optical steadiness of the 

 atmosphere. A remarkable experience of m}^ 

 own on the mountain ma}' be mentioned here. 

 On the night of the 2d of December, 1882, 

 when the wind was blowing stead il}' with such 

 violence as to make it extremely hazardous 

 to open the dome in the face of it, I found 

 Jupiter and Saturn very unsteady and much 



