INOS ET SMITHSONIAN EXPEDITIONS, IQIO-1911 5 
California (4,420 meters). It is rather a new departure with the 
bolometer, that delicate instrument which measures the millionth of 
a degree rise of temperature, to use it out of doors, following the sun 
in an equatorial telescope, but Mr. Abbot successfully used it so in 
1908 at Flint Island in the South Pacific, in 1909 and 1910 at Mount 
Whitney, and now for several months in 1911 in Algeria. 
A delay of about 2 weeks occurred in beginning observations, 
owing to the miscarriage of one of the cases of apparatus. Consider- 
able cloudy weather unfortunately prevailed in September and Octo- 
ber, both at Bassour and at Mount Wilson, California, where Mr. L. 
Fic. 2.—Spectrobolometer. Photograph by Abbot. 
B. Aldrich was conducting similar observations. Messrs. Abbot and 
Brackett observed on 44 days at Bassour, and discontinued observing 
on November 18. Mr. Aldrich observed on 29 of these days at 
Mount Wilson, and secured observations for about four more which 
will be useful for the comparison of results between the two stations. 
It takes about three days of computing to reduce one day’s observa- 
tions, so that the final results of the work are not yet known. If 
further experiments are necessary, it is hoped to make them at the 
same stations in June, July, and August of 1912. 
Recent experiments of the Smithsonian Astrophysical Observatory 
made principally at Mount Wilson, California, in the years 1905 to 
