274 SCIENCE PROGRESS 



The belief is found already in the Zend-Avesta and again in 

 a number of Greek and Roman authors. Connected with the 

 same notion is the conception of the moon as a source of moisture 

 and thus an aid to plant growth. Plutarch says that " dew 

 falls most at full moon," and in another place, when speaking 

 of Osiris as a moon-god, refers to " his humid and generative 

 light favourable to the growth of plants." The same function 

 was ascribed to the Greek Artemis. 



The supposed role of the moon as a source of moisture seems 

 to derive from the fact that there is most radiation from the 

 ground and hence the greatest deposit of dew on cloudless 

 nights. The moon has no effect on the cloudiness or otherwise 

 of the sky — ^meteorologists are decided on this point, in spite of 

 the saying of sailors that " the moon eats up the clouds " — 

 but it is on cloudless nights only that the moon is visible, and it 

 is just on these nights that dew is formed. Thus the dew is 

 credited to the moon. So gardeners fear the April moon, for 

 at this season excessive radiation injures young shoots by 

 reducing their temperature unduly. This occurs on cloudless 

 nights, which are most noticeable when there is a moon to light 

 the sky. 



There is an ancient belief and one that is widespread to-day 

 that sowing and planting must be done under a waxing, reaping 

 and cutting under a waning moon. Presumably the crops are 

 supposed to be increased like many other things by the growing 

 moon. The idea lying behind harvesting or felling timber 

 beneath a waning moon is more difficult to trace, but may be 

 connected with the drying influence which is ascribed to the 

 declining phases in the same way as dew is attributed to the 

 waxing and full moon. At all events the belief is most wide- 

 spread that wood for building purposes is not durable unless cut 

 after the full moon, and indeed until the Revolution French law 

 ordained that trees should be felled only under a waning moon. 

 In Trinidad, where the belief is strongly held, experiments were 

 recently made which demonstrated the absence of any basis 

 of truth to the superstition. 



> Passing now to animals, it is principally on marine inverte- 

 brates that the moon is said to exert an influence. There are 

 a number of references to this in the classical authors. Aris- 

 totle says that the ovaries of sea-urchins acquire a greater size 

 than usual at the time of full moon. Cicero notes that " oysters 

 and all shell-fish increase and decrease with the moon," and 

 Pliny states that " careful observers attribute to lunar power 

 the increase and decrease of the bodies of oysters and all 

 shell-fish." The same behef is common to-day in many of the 

 fish-markets around the Mediterranean and in other parts of 

 the world. The amount of edible matter in sea-urchins. 



