8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



ing. It was proposed also to make pyrheliometric observations dur- 

 ing the days on the top of Mount Whitney. These latter measure- 

 ments, which are taken as a basis for determinations of the solar 

 constant are given in an appendix written by Dr. Kennard and 

 myself. 1 



The Mount Whitney part of the expedition was regarded as by 

 far the most important, both on account of the higher altitude of the 

 station, and because of the conveniences presented by the position 

 on the top of the mountain, which made it possible to observe there 

 during a considerable interval of time. Mount Whitney is too well 

 known through the expedition of Langley (in 1881) and of Abbot 

 (in 1909 and 1910) to need any description here. In the year 1909, 

 the Smithsonian Institution erected — on the suggestion of Directors 

 Campbell and Abbot — a small stone house on the summit as a shelter 

 for future observers. Permission was given me by the Smithsonian 

 Institution to use this shelter for the purposes of the expedition. 



As the observations were to be made simultaneously in different 

 places, several observers were needed. At this time (in the begin- 

 ning of the year 1913) I was engaged in some investigations at the 

 physical laboratory of Cornell University, Ithaca, N. Y„ and from 

 there I was enabled to secure the services of my friend, Dr. E. H. 

 Kennard, as a companion and an able assistant in the work of the 

 expedition. Further, Prof. F. P. Brackett, Director of the Astro- 

 nomical Observatory of Pomona College, Claremont, California, 

 promised his assistance, as also did Professor Williams and Mr. 

 Brewster from the same college. 



On the 8th of July, 191 3, the author and Dr. Kennard arrived 

 at Claremont, California, where Messrs. Brackett, Williams, and 

 Brewster joined us. Through the kindness of Prof. Brackett the 

 excellent little observatory of Pomona College was placed at my 

 disposal as headquarters, and here the assistants were instructed, 

 and the instruments — galvanometers, actinometers and ammeters — 

 were tested. 



On the 1 2th of July the first preliminary expedition was made, 

 when the author and Mr. Brewster climbed to the summit of 

 Mount San Antonio, the highest peak of the Sierra Madre Range 

 (3,000 m.) and observed there during the two following nights. 

 At the same time Prof. Brackett and Dr. Kennard observed at 

 Claremont at the foot of the mountain, but unfortunately at the 



1 This paper has also appeared in the Astrophysical Journal, Vol. 39, No. 4, 

 May, 1914. 



