THE MOON AND THE WEATHER. 



losophical observers, and to perceive that the appearances referred to were by 

 them regarded merely as signs, prognosticating (whether truly or not we shall 



\ see presently) approaching changes, and not at all as physical causes effecting 



c these changes. 



; We shall limit ourselves to a few of the more remarkable and generally re- 



< reived ancient meteorological maxims, as examples of the whole. 



f' In the work of Aratus, entitled Aioff^fAS/a (prognostics'), and in the Scho- 

 lia of Theon, and elsewhere, the appearances of the moon in different phases 

 are described as prognosticating the weather for a certain time to come : 



5' oDr 1 ' flrarfiv sic' ij/jiao'i TTavra rirvxrau. 



"AX.X' Otfa /JLSV TPITOCTTJ TETparaiTJ T6 



ys (xsv 



X <5yf 



5s oi aur 



M^voj owroiyo/ASvou. APAT 



Sin ortu quarto (namque is certissimus auctor), 

 Pura, neque obtusis per crelum cornibus ibit, 

 Totus et ille dies, et qui nascentur ab illo, 

 Exactum ad mensem pluvia ventisque carebunt. 



VIRGIL, Georg., Lib. I., 1. 432. 



If the horns of the lunar crescent on the third day after new moon are sharply 

 and clearly defined, the weather may be. expected to be fair during the ensuing 

 month. 



Let us see how far this prognostic will stand the test of rational examina- 



ion. The lunar crescent is produced by a peculiar relation of position which 

 subsists between the aspects of the moon presented to the sun and earth. If 

 only half the hemisphere which receives the sun's light be presented toward 

 the earth, the moon is exactly halved ; if a quarter of the hemisphere be turned 

 to the earth, the moon is crescent, and its age is then nearly four days. When 

 its age is less than two days, therefore, less that one eighth of its illuminated 



lemisphere is presented to our planet, and consequently it appears a very thin 

 crescent. It is evident that these effects, if seen through perfectly transpa- 

 rent space, could not alter with circumstances, and that, in the same position 

 of the moon with respect to the earth and sun, the crescent must be at all times 

 equally sharp and distinct. But when the moon is viewed (as it is by us) 

 through an atmosphere that is from thirty to forty miles high that atmosphere 



jeing liable to be more or less loaded with imperfectly transparent vapors it 

 will be seen with more or less distinctness, according to the varying transpa- 

 rency of the medium through which it is viewed. The fact, therefore, of the 

 crescent appearing distinct and well defined, or obscurely, with the points of 

 the horns blunted, is merely in consequence of our atmosphere being at one 

 time more pure, clear, and transparent, than at another. 



When the moon is under three days old, it is only visible for a short time 

 after sunset, and therefore the phenomenon in question can only be observed in 

 the evening, a little above the western horizon. This prognostic of Aratus 

 may be thus translated : " When the atmosphere above the western horizon 



' soon after sunset on the third day of the moon is serene, the weather will be 



' fair for the remainder of the. month ; but if it be loaded with vapors, the con- 



' trary event will ensue." 



All the world, says Arago, will doubtless reject the prognostic when thus 

 stated ; nevertheless, the words only in which it is expressed are changed, the 

 meaning being absolutely the same. 



