258 



CARNEGIE INSTITUTION OF WASHINGTON. 



very good. In June and July, 37 consecutive full nights were secured, 

 and in August there were but 8 hours of interruption by clouds. A 

 record of the seeing, on a scale of 1 to 5 (the latter being perfect), is 

 shown herewith, together with the wind-record from Mr. Hoge's 

 observations : 



The wind percentages, which are somewhat more favorable than 

 those of the preceding year, are: high, 7; brisk and moderate, 25; 

 light to calm, 68. 



The average change of temperature in the dome between the time 

 of opening in the late afternoon and of closing in the morning was 5°. 9 C. 

 The highest temperature recorded was 30°. 4 C. on August 13, while the 

 lowest was — 4°.0 C. on January 27. 



DIRECT PHOTOGRAPHY. 



During the year Mr. Pease obtained the following photographs at the 

 principal focus of the 60-inch reflector: 



spiral nebulae 



Spindle nebulae 



Nebulae with bright center in nebu- 

 lous mass with no detail 



Irregular nebulae 



N. G. C. 972, 4567-8, 5740, 7217. 



N. G. C. 955, 4388, 4402, 4425, 4564. 5476. 



. N. G. C. 4374, 4387, 4406. 

 N. G. C. 1555. 1579. 2264. 



Star clusters Additional plates of M 13 and M 15 for 



counting; N. G. C. 67G0. 



Five plates SO far have been obtained of the region of N. G. C. 1555, 

 Hind's Variable Nebula in Taurus. No change can be detected not 

 attributable to differences in the quality of the plates. 



Two plates have been taken of N. G. C. 6760, described by recent 

 observers as a variable nebula. The photograph of 1^ hours' exposure 

 on a Seed 27 plate shows it to be an irregular circular cluster 7 minutes 

 in diameter containing about 1200 stars ranging approximately from 

 16.5 to 19.5 photographic magnitude, superimposed on a background 

 whose average density is 15 stars per square minute. No trace of 

 nebulosity is found. 



Miss Van Deusen has counted the stars on photographs of a number 

 of clusters made by Mr. Pease. Owing to conditions of seeing, distance 

 from the zenith, and the difference in plate emulsions, it is often the case 

 that a shorter exposure will contain more stars than a longer one, but 



