LUNAR INFLUENCES. 475 



Among the maxims of Pliny we find that grapes should be dried by night at 

 new moon, and by day at full moon. 



When the moon is new it is below the horizon during the night, and above 

 it during the day ; and when it is full it is above the horizon during the night, 

 and below it during the day. The maxim of Pliny, therefore, is equivalent to 

 a condition requiring that the grapes should be dried when the moon is below 

 the horizon. It is evident that the absence of the moon is not required in this 

 case in consequence of any effect which her light might produce if she were 

 present ; for when the moon is new she affords no light, even when in the fir- 

 manent, the illuminated side being turned from the earth. If the maxim be 

 founded upon any reason, it must, therefore, either be on some influence which 

 the moon is supposed to produce when present, independent of her light (the 

 absence of which influence is desired), or it may be that she may be supposed 

 to transmit some effect through the solid mass of the earth when on the other 

 side of it which she is incapable of producing without its intervention. The 

 maxim is probably as absurd and groundless as the other effects imputed to the 

 moon. 



Supposed Lunar Influence on the Complexion. It is a prevalent popular no- 

 tion in some parts of Europe, that the moon's light is attended with the effect 

 of darkening the complexion. 



That light has an effect upon the color of material substances is a fact well 

 known in physics and in the arts. The process of bleaching by exposure to the 

 sun is an obvious example of this class of facts. Vegetables and flowers which 

 grow in a situation excluded from the light of the sun are different in color 

 from those which have been exposed to its influence. The most striking in- 

 stance, however, of the effect of certain rays of solar light in blackening a light 

 colored substance, is afforded by chloride of silver, which is a white substance, 

 but which immediately becomes black when acted upon by the rays near the 

 red extremity of the spectrum. This substance, however, highly susceptible 

 as it is of having its color affected by light, is, nevertheless, found not to be 

 changed in any sensible degree when exposed to the light of the moon, even 

 when that light is condensed by the most powerful burning lenses. It would 

 seem, therefore, that as far as any analogy can be derived from the qualities of 

 this substance, the popular impression of the influence of the moon's rays in 

 blackening the skin receives no support. 



M. Arago (who generally inclines to favor rather than oppose prevailing 

 popular opinions), appears to think it possible that some effect may be pro- 

 duced upon the skin exposed on clear nights, explicable on the same principle 

 as that by which we have explained the effects erroneously imputed to what is 

 called the red moon. The skin being, in common with the leaves and flowers 

 of vegetables, a good radiator of heat, will, when exposed on a clear night, for 

 the same reasons, sustain a loss of temperature. Although this will be to a 

 certain extent restored by the sources of animal heat, still it may be contended 

 that the cooling produced by radiation is not altogether without effect. It is 

 well known that a person who sleeps exposed in the open air on a night when 

 the dew falls, is liable to suffer from severe cold, although the atmosphere around 

 him never falls below a moderate temperature ; and although no actual depo- 

 sition of dew may take place upon his skin. This effect must arise from the 

 constant lowering of temperature of the skin by radiation. In military cam- 

 paigns the effects of bivouacking at night appear to be generally admitted to 

 darken the complexion.* 



* Le hale de bivouac is an effect quite recognised. Hale is a term which expresses a state of the 

 air which makes an impression upon the complexion, rendering tanned and burnt. 



