v BELIEF AND EVIDENCE 99 



The subject has been investigated in other countries 

 than Great Britain. Observations of the night sky at 

 Potsdam for the six years from 1894 to 1900 failed to 

 show any cloud- dispersing power for the Full Moon. 

 It was found, indeed, that there was a maximum amount 

 of cloud visible shortly after Full Moon and a minimum 

 about the time of New Moon. This result is to be 

 expected if the moon has no influence upon clouds ; 

 for moonlight makes clouds visible. At Kenilworth 

 (Kimberley) Mr. J. R. Button has found that certain 

 clouds appear to dissolve at sunset, but the rising moon 

 makes them visible again. Observations made at 8 p.m. 

 over a period of seven years show considerably more 

 cloud between the third and eighteenth days of the 

 moon's age than between the eighteenth and third, so 

 that here again the evidence is opposed to the popular 

 view. At any rate, we are justified in declining to accept 

 the power of the moon to disperse clouds until proof of 

 this capacity is forthcoming from those who believe in it. 



As the moon is chiefly responsible for the rise and fall 

 of the tides, it seems reasonable to suppose that the 

 earth's atmosphere is affected in the same way, and that 

 there are air-tides which may vary through the lunar 

 month, like the spring and neap tides of the sea. Daily 

 atmospheric tides due to the moon have, in fact, been 

 detected in records of barometer readings made at 

 Brest, St. Helena, Cape Horn. Batavia, and Singapore. 

 In 1895 M. Bouquet de la Grye proved that the curves 

 of atmospheric pressure obtained at these places show 

 clearly a regular ebb and flow twice a day in accordance 

 with the position of the moon. The effect, however, is 

 of a very minute character. The maximum difference 

 attributed to the influence of the moon is about one- 

 fiftieth of an inch in the height of the mercury in a 



