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ON THE LUNAR CLOUD-PERIOD. 



By J. R. Sutton, M.A. 



(Read July 31, 1907.) 



Herr Otto Meissner has recently raised anew the question of the 

 pretended cloud-dispersing power of the moon. In a discussion of 

 the observations of the state of the night sky made at Potsdam 

 during the eighty lunations extending from January, 1894, to June, 

 1900, he finds no such dispersing power, but, on the contrary, a 

 minimum of cloud about the time of new moon, and a maximum at 

 or shortly after full." A summary of the mean percentages of sky 

 obscured by cloud at Potsdam for the three observation-hours 



Q ^n ^ ■;,-i.,(- XXI. + XXII. + XXIV. \ , 

 y p.m., 10 p.m., and midnight U.e., ^ J, tor 



each day during the lunar month, is given in the large Table at the 

 end of this paper. The following is a reduction of the result : — 



Moon's Age. 



Cloud per cent 



Day 1-3 



57 



4-6 



53 



7-9 



59 



10-12 



63 



13-15 



59 



16-18 



68 



19-21 



58 



22-24 



59 



25-27 



57 



28-30 



55 



These numbers appear to indicate that the sky is clearest in the 

 first week, and most obscured in the third week of a lunation. 



* 0. Meissner, " Ueber die angebliche ' wolkenzerstreuende ' Kraft des Mondes,'* 

 Blet. Zeitschrift, May, 1907. 



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