Scientific InteUtgence. — Meteorology. 199 



four, five or six centigrade degrees above zero. When this hap- 

 pens, 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, unless the thermometer indicates zero. It is 

 therefore quite true, as the gardeners pretend, that under ther- 

 mometrical circumstances precisely alike, a plant may be frozen 

 or not, according as the moon may be visible or concealed be- 

 hind clouds. If they are deceived, it is only in their conclu- 

 sion in attributing the effect to the light of the moon. The 

 moon^s light is, in this case, only the index of a clear atmo- 

 sphere ; it is only in consequence of the clearness of the sky that 

 the nocturnal congelation of plants takes place, the moon con- 

 tributes to the effect in no way whatever ; although she were 

 hid under the horizon, the effect would not be different. 



3. Influence of the Moon on Diseases, — Hippocrates, says 

 Arago, had so lively a faith in the influence of the stars on ani- 

 mated beings, and on their maladies, that he very expressly re- 

 commends not to trust to physicians who are ignorant of astro- 

 nomy. The moon, however, according to him, only acted a secon- 

 dary part, the preponderating stars were the Pleiades, Arcturus 

 and Procyon. Galen shewed himself, in this respect, a zealous 

 disciple of Hippocrates ; but it was the moon to which he as- 

 signed the chief influence. Thus the famous critical days in 

 diseases — that is to say, the 7th, the 14th, and the 21st, were 

 connected with the duration of the principal phases of our satel- 

 lite, and the lunar influence became the principal pivot of the 

 system of C7ises. With regard to the theory of lunar influence 

 on disease, it still counts a goodly number of partisans. In 

 truth, I know not if the circumstance ought to astonish us. 

 Is it not something to have on our side the authority of the two 

 great physicians of antiquity ; and among the moderns, that of 

 Mead, Hoffman, and Sauvage ? Authorities, I admit, are of 

 little weight in matters of science, in the face of positive facts ; 

 but it is necessary that these facts exist, that they have been 

 subjected to severe examination, that they have been skilfully 



