ON THE APPEARANCES AND INFLUENCES OF THE MOON. 837 



judices, 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 substances, 

 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 ascertained. On placing little masses 

 of cotton down, &c., in the open air, it is frequently observed that 

 they acquire a temperature of six, seven, or 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 affected during the night by the indications of a ther- 

 mometer suspended in the free atmosphere ; the plant may be strongly 

 frozen, although the air remains constantly several degrees 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 thermometer, when the sky is perfectly clear. If the sky 

 is clouded, they become insensible. 



Is it now necessary to point out the connection between these pheno- 

 mena, and the opinions of the country people regarding the April 

 moon? 



In the nights of April and May, the temperature of the atmosphere 

 is frequently only four, five, or six centigrade degrees above zero. When 

 this happens, plants exposed to the light of the moon that is to say, 

 to a clear sky may be frozen notwithstanding the indications of the 

 thermometer. If the moon, on the contrary, does not shine, in short, 

 if the sky is cloudy, the temperature of the plants does not fall below 

 that of the atmosphere ; and they will consequently not be frozen, un- 

 less the thermometer indicates zero. It is therefore quite true, as the 

 gardeners pretend, that under thermometrical circumstances precisely 

 alike, a plant may be frozen or not, according as the moon may be visible 

 or concealed behind the clouds. If they are deceived, it is only in their 

 conclusion, in attributing the effect to the light of the moon. The moon's 

 light is, in this case, only the index of a clear atmosphere ; it is only 

 in consequence of the clearness of the sky, that the nocturnal congelation 

 of plants takes place ; the moon contributes to the effect in no way 

 whatever ; although she were hid under the horizon, the effect would 

 not be different. 



A body exposed to the light of the moon, that is to say, to a clear 



