1 68 



CARNEGIE INSTITUTION OF WASHINGTON. 



WIND MOVEMENT. 



With such uniformity of atmospheric pressure, it might naturally 

 he anticipated that the wind movement would be low. The results of 

 anemometer readings (in miles), made with an instrument of the 

 standard Weather Bureau pattern, are shown in the following table. 

 The "day" results give the total movement from 8 a. m. to 6 p. m. ; the 

 "night" results give the total movement from 6 p. m. to 8 a. m. 



Day 



of 



month. 



I.. 



2.. 



3-- 

 4- 

 5" 

 6.. 



7" 

 8.. 



9- 



10.. 



11.. 



12.. 



13.- 

 14.. 

 15-. 

 16.. 



17.. 

 18.. 

 19.. 

 20.. 

 21.. 

 22.. 



23-. 

 24.. 



25-- 



26.. 

 27.. 

 28.. 



29" 



30" 

 31- 



Total. 



Mean 



Hourly mean. 



April. 



Day. 



140 

 62 



35 

 40 



47 

 32 

 70 



91 

 44 



33 

 50 

 47 



691 



57-6 

 5-8 



Night. 



188 

 70 



144 

 42 



120 



109 



63 

 191 



51 



34 



lOI 



63 



1,176 



96.0 

 6.8 



May. 



Day. 



99 

 49 

 52 

 29 

 43 

 30 

 34 

 43 

 38 

 44 

 54 

 35 

 41 

 39 

 72 

 42 

 46 



50 

 105 

 45 

 63 

 66 



67 

 69 

 63 

 33 

 50 

 21 

 62 

 51 

 57 



1.592 



51-3 

 5-1 



Night. 



165 

 iiS 



88 



91 

 62 

 128 

 106 

 44 

 1.^3 

 no 



lOI 



80 



95 

 114 

 no 



81 



56 



136 



48 



71 

 82 



97 



79 



136 



60 



58 

 loi 



73 

 80 



151 



2,929 



94.5 

 6.7 



June. 



Day. 



71 

 44 

 44 

 61 



78 

 59 

 55 

 50 

 52 

 43 

 32 

 30 

 23 

 49 

 56 

 40 



37 

 30 

 36 

 56 

 37 

 74 

 44 

 52 

 55 

 75 

 42 

 37 

 56 



1.538 



51-3 



5-1 



Night. 



175 

 141 

 185 

 114 



47 

 108 



'55 



146 

 66 

 86 

 49 

 75 

 95 



133 

 61 

 80 

 58 

 56 

 47 

 74 

 90 

 56 



103 

 86 

 51 

 59 

 51 

 52 

 60 

 46 



2,605 



86.6 

 6.2 



July- 



Day. 



55 

 71 

 47 

 34 

 30 



43 

 40 



49 

 44 

 43 

 49 

 31 

 42 

 42 

 39 

 33 

 40 



32 



38 

 63 

 37 

 43 

 44 

 60 



44 

 39 

 47 

 41 

 56 

 57 

 53 



1,386 



44-7 

 4-5 



Night. 



145 

 102 



71 

 41 



54 

 78 

 44 

 85 

 83 

 77 

 93 

 74 

 81 



59 

 68 

 50 

 70 

 62 

 78 

 91 

 60 



37 

 85 

 64 

 56 

 71 

 80 



57 



65 



131 



97 



2,309 



74-5 

 5-3 



August. 



Day. 



43 

 50 



45 

 46 

 60 

 43 

 47 

 33 

 43 

 62 



49 

 58 

 59 

 44 

 44 

 45 

 44 

 26 



37 

 36 

 39 

 63 

 63 

 55 

 50 

 35 

 56 

 54 

 55 

 57 

 38 



1.479 



47-7 

 4.8 



Night. 



95 

 72 

 61 

 48 

 41 

 49 

 80 



63 

 60 

 78 

 81 



122 

 71 

 73 

 55 

 80 

 60 

 55 

 58 



100 



55 

 104 



113 

 loi 

 64 

 66 

 84 

 107 

 56 

 69 

 54 



2.275 



73-4 

 5-2 



It appears from these results that the average wind movement 

 IS exceptionally low. The importance of this fact in its indication 

 of a uniform atmosphere, and in connection with astronomical 

 photography, will be appreciated by astronomers. The shaking 

 of a large instrument by the wind is frequently so serious as to 

 reduce greatly the quality of astronomical photographs obtained 

 in windy weather. At Mount Wilson, where a dead calm is an ex- 

 ceedingly common occurrence, all of the most exacting requirements 

 of astronomical photography are completely realized. 



