ASTKOPHYSICS IN THE UNITED STATES BOSLER. 365 



tence of people on the planet ; but here, also, we must note, there are 

 divergencies of opinion, and we must not insist. 



The ingenious methods of Lowell have been applied as well to 

 Jupiter and Saturn; they have revealed on the equatorial bands of 

 these two planets curious oblique filaments, a sort of network (re- 

 seau) of cells which had already been noted in visual observations, 

 but the interpretation of which has not yet been found. 



Whatever we may think of the theoretical and philosophical ideas 

 of which Lowell is the brilliant champion, there is no doubt that his 

 methods present an important advance; in every way his planet 

 photographs are among the best, perhaps the best, which have been 

 made. 



MOUNT WILSON OBSERVATORY — SOLAR PHYSICS. 



At Mount Wilson we are brought more especially to the study of 

 the sun. The Mount Wilson Solar Observatory was founded in 1904 

 through the munificence of Mr. Andrew Carnegie and at the request 

 of Dr. Hale, then director at the Yerkes Observatory. Hale was 

 especially interested in finding for solar physics a very elevated sta- 

 tion where the atmospheric disturbances and convection currents 

 Avould be less noticeable; therefore it seemed to be necessary to seek 

 such a place among the mountains of the Pacific coast, which had 

 been shown to be so favorable for astronomical researches. After 

 a detailed inquiry at various places Hale chose Mount Wilson, a few 

 hours' ride from Pasadena, not far from Los Angeles, a peak of 1,800 

 meters altitude and crowned with pines; he had transported there a 

 portion of the instruments which he had used at the Yerkes, taking 

 with him also several of his assistants. 



At the foot of the mountain in the village of Pasadena are situated 

 the offices for measurements and calculations. Here, as everywhere in 

 America, there is a personnel exclusively feminine, which is an ad- 

 vantage where, initiative being secondary, care and delicacy are 

 required. Finally, in order to reap results from the greatest possible 

 number of plates, a stereo-comparator by Zeiss is used. This is a 

 German device, allowing the exact superposition and the changing at 

 will in the field of vision of two slightly different plates of the same 

 legion ; the smallest divergencies, the smallest changes, are then easily 

 noted. 



We find here also an admirably organized workshop provided 

 with all American mechanical resources, which means that they do 

 here with mechanical means many things that we still do by hand, 

 resulting in a great saving of time. Finally — and this is a thing of 

 capital importance — these machines allow the working of pieces of 

 very great dimensions which could never be executed in the shops of 

 the best French constructors of astronomical instruments. 



