226 Mr. J. P. Harrison Lunar Influence on Temperature. [May 4, 



apparent paradox of heat occurring at the moon's first quarter suggested 

 itself in 1857*. 



It was evident that the effects noticed could not he due to any heat 

 derived directly from the moon. Even if the experiments of Melloni and 

 Bouvard and, it may he added, the results obtained by Professor Piazzi 

 Smythe on Teneriffe had not established it as a fact that no serviceable 

 heat, dark or luminous, reaches the lower strata of the earth's atmosphere 

 at the period of full moon, the results of the tabulation of mean temperatures 

 at various stations and for different periods of time show that, with some 

 remarkable exceptions to be hereafter accounted for, cold displays itself on 

 the average in the second half of the lunation, and a higher temperature 

 at first quarter at the very time when it may be supposed that the moon 

 has parted with the whole of the heat she has received from the sun, and 

 her crust opposite the earth has not been subjected to the solar rays for a 

 sufficiently long period for lunar radiant heat to exercise any thermal 

 action, either direct or indirect, on our atmosphere. 



This being so, the concurrent results of investigations undertaken by 

 eminent physicists in this and other countries point to a maximum of cloud, 

 rain, and vapour-bearing winds in the first half of the lunation, when the 

 curves indicate heat f ; and a minimum of cloud and rain, with drier winds, 

 in the second half of the lunation. It was not difficult then to connect the 

 two phenomena all gardeners being practically aware of the fact that heat 

 is retained in the soil by the agency of cloud %, Professor Tyndall has 

 shown by his elaborate experiments, that this is the case also with respect 

 to the aqueous vapour of the atmosphere. 



Whether the dispersion of Cloud is due to the Radiant heat of the 

 Moon. As regards the degree of heat which is attained by the moon, Sir 

 John Herschel estimates it as equal to the boiling-point of water ; and the 

 same eminent person considers that the radiation of this heat would be 

 sufficient to disperse cloud in the upper regions of the air. 



The estimate of the moon's heat appears to be that of our satellite at 

 the period of opposition. But the maximum heat would not be attained 

 until several days later ; for, the moon always turning the same face to the 

 earth, her crust directly opposite to us does not attain its greatest heat 

 until last quarter, at which time not only will it have received the sun's 

 rays for twice the number of days during which that surface had been 

 heated at the time of opposition, but the adjoining region also (eastward 

 of it), itself recently illuminated and heated for fourteen, thirteen, and 

 twelve times the length of our day of twenty -four hours, although the sun's 



* See Brit. Assoc. Reports, 1857, p. 248. 



t The number of clear and cloudy days at Greenwich, during the seven years (1841-47) 

 that bihourly observations were made at that station, also corresponds with the hot and 

 cold periods at the station. 



J See also Mr. Glaisher's paper on the subject in the Philosophical Transactions. 



