ASTRONOMY — HALE. 69 



HOOKER EXPEDITION'. 



As the result of a special gift made by Mr. John D. Hooker, of Los 

 Angeles, for this purpose, Professor Baruard was enabled to bring 

 the Bruce telescope from the Yerkes Observatory to Mount Wilson 

 in December, 1904, and to carry on photographic work with it until 

 the completion of his program in September, 1905. Although the 

 work is to be considered as that of the Yerkes Observatory, I 

 may be permitted to say a few words regarding it in the present 

 report. Professor Barnard's special object was to photograph the 

 southern part of the Milky Way, in the region that can not be reached 

 from the latitude of Williams Bay. He has accomplished this pur- 

 pose in a most satisfactory manner, with the same untiring zeal that 

 he has shown in all his undertakings. The perfection of the photo- 

 graphs, testifying at once to the skill of the observer, the excellence 

 of his instruments, and the purity of the sky, must be seen to be 

 appreciated. They include not only the large plates made with the 

 10-inch Brashear lens, but also three complete series of smaller plates, 

 made with a powerful battery of lenses, all working simultaneously. 

 In addition to his photographic observations in the southern heavens, 

 Professor Barnard has made many valuable plates of northern objects. 

 It is hoped that provision will be made for the early publication of 

 these results, as they constitute a most important contribution to our 

 knowledge of the structure of the Milky Way and of the remarkable 

 nebulae within it. 



SMITHSONIAN EXPEDITION. 



The inception of the Solar Observatory was due to a suggestion 

 made by Secretary Langley, of the Smithsonian Institution, regarding 

 the desirability of providing for systematic observations of the solar 

 radiation at a mountain station. The work of the Smithsonian 

 Observatory during the last few years has emphasized this suggestion 

 by indicating the probability that the solar constant has undergone 

 considerable variations. Furthermore, these variations nearly 

 coincide in time with apparent changes in the absorbing power of 

 the solar atmosphere and in the mean temperature of the earth's 

 atmosphere. So important a conclusion deserves the most complete 

 investigation, such as might result from a simultaneous attack with 

 similar apparatus from Washington and Mount Wilson. As Mr. 

 Langley had planned to send an expedition to some mountain station 

 for this purpose, it was a special pleasure to place at his disposal all 

 the facilities that could be offered by the Solar Observatory. He 



