132 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



\0L. 66 



from tlay to day, but the average values found in a whole season's 

 work, vary from year to year. 



It was primarily to continue and amplify these* studies of the 

 solar variability that the observing' was done on Mount Wilson in 

 1916. l)Oth the total radiation of the sun and the distribution of 

 brightness over the solar disk were measured on as large a number 

 of days as possible. Owing to considerable cirrus cloudiness in 

 June and August, a dense haze suggesting the volcanic haze of 



Fig. 128. — Observers' cottage and solar cooker, Mount Wilson, California. 



191 2 in late July and early August, and to heavy rains in late Sep- 

 tember and early October, the season proved less favorable than 

 usual, but nearly 100 days of observation were secured. Full reduc- 

 tion of the observations must be awaited before noting the solar 

 changes during the season, but generally high values of solar radia- 

 tion seemed to prevail, as was expected in view of numerous sun- 

 spots. At one time in June nearly 100 spots were seen on the sun's 

 image. Large magnetic disturbances were associated with this spot 

 outbreak, and observations had to be suspended on one day because 

 of them. 



