190 Scientific Intelligence. — Meteorology. 



fluence on the young shoots of plants. They maintain that they 

 have observed during the night, when the sky is clear, the leaves 

 and buds exposed to this light, to become red, that is to say, to 

 be frozen, although the thermometer in the free atmosphere 

 stood several degrees above the freezing point. They also as- 

 sert, that if the rays of the moon are intercepted by clouds, and 

 thereby prevented from reaching the plants, the same effects do 

 not take place, under circumstances perfectly similar in other 

 respects with regard to temperature. These phenomena seem 

 to indicate that the light of our satellite is endowed with a certain 

 frigorific influence ; yet, on directing the most powerful burning- 

 glasses, or the largest reflectors towards the moon, and placing the 

 most delicate thermometers in their foci, no eff^ect has ever been 

 observed which could justify so singular a conclusion. Hence 

 with philosophers the eff*ects of the April moon are now referred 

 to the class of vulgar prejudices, while the gardeners remain 

 convinced of the accuracy of their observations. A beautiful 

 discovery made some years ago by Dr Wells, will enable us, I 

 think, to reconcile two opinions in appearance so contradictory. 

 No one had supposed, before Dr Wells, that terrestrial sub- 

 stances, excepting in the case of a very rapid evaporation, may 

 acquire during the night a different temperature from that of 

 the surrounding air. This important fact is now well ascer- 

 tained. On placing little masses of cotton, down, &c. in the 

 open air, it is frequently observed that they acquire a tempera- 

 ture of six, seven, or even eight centigrade degrees below that 

 of the surrounding atmosphere. The same is the case with 

 vegetables. We cannot therefore judge of the degree of cold 

 with which a plant is aff*ected during the night, by the indica- 

 tions of a thermometer suspended in the free atmosphere : the 

 plant may he strongly frozen^ although the air remains constant- 

 ly several degi-ees above the freezing point. These differences 

 of temperature between solid bodies and the atmosphere only 

 rise to six, seven, or eight degrees of the centesimal thermome- 

 ter, when the sky is perfectly clear. If the sky is clouded they 

 become insensible. Is it now necessary to point out the con- 

 nexion between these phenomena, and the opinions of the coun- 

 try people regarding the April moon ? In the nights of April 

 and May, the temperature of the atmosphere is frequently only 



