238 



CARNEGIE INSTITUTION OF WASHINGTON. 



when a maximum velocity of 90 miles per hour was recorded at the 

 top of the 150-foot tower telescope. The gale lasted for 52 hours, 

 during which time the average velocity was 50 miles per hour. For 

 one period of 5 hours an average velocity of 75 miles was maintained. 

 All of the buildings of the Observatory withstood the gale without 

 damage, but several large pine trees near the 100-inch dome were up- 

 rooted. The average wind velocity for the year was 11 miles per hour. 

 The highest temperature for the year was 100° F., on August 21, the 

 highest on record; the lowest was 16° F. on December 31. The tables 

 give statistics for each month, the conditions of seeing (on a scale of 

 10), and the wind velocity. 



Month. 



Hours of 

 darkness. 



Hours 

 clear. 



Hours 

 cloudy. 



Hours lost 



silvering 



and repairs, 



Hours of 



exposure 



time. 



Observations. 



All 



night. 



Part of 

 night. 



None. 



1918. 

 September . 



October 



November . 

 December . 



1919. 

 January . . . 

 February . . 



March 



April 



May 



June 



July 



August .... 



295 

 336 

 330 

 346 



346 

 308 

 324 

 286 

 266 

 230 

 255 

 269 



Totals for year. 

 Mean for 7 

 years 



3,591 



203 

 216 

 168 

 204 



187 

 129 

 188 

 174 

 193 

 230 

 235 

 251 



92 

 119 

 162 

 142 



159 



179 



136 



103 



3 



70 



20 



18 



129 

 134 

 104 

 144 



140 

 93 

 135 

 139 

 132 

 173 

 165 

 170 



16 

 14 

 13 

 13 



9 

 7 

 11 

 16 

 21 

 30 

 27 

 27 



2,378 

 2,298 



1,203 

 1,286 



10 



1,658 

 1,623 



204 

 191 



10 



13 



7 



11 



15 

 10 

 14 

 6 

 4 

 

 4 

 3 



97 

 92 



4 



4 



10 



7 



7 

 11 



64 



82 



PHOTOGRAPHS OF NEBULAE AND CLUSTERS. 



Mr. Pease has duplicated with the 60-inch reflector many photo- 

 graphs of nebula3 taken in 1917-18 and has obtained negatives of the 

 following additional objects: 



