of Climate caused by the Moon. 



435 



The Tables (I. & II.) of monthly mean temperatures and atmo- 

 spheric pressures during that period of 27 years show that the 

 highest annual temperature was in 1863 8°*705 R., the lowest 

 in 1855 6°*389, the average of the extremes being 7°*599 R. 

 The years showing nearly the mean annual temperature of 7°*599 

 were the following : — 





Average. 



Difference. 



Period. 



1842. 



1848. 

 1857. 

 1865. 



7-642 

 7490 

 7-614 

 7-614 



+0 043 

 -0-109 

 +0015 

 +0015 



7 years. 

 10 „ 

 9 n 



The mean period is 8-7 years; during that time the annual 

 temperature repeatedly reaches twice the average of the extremes ; 

 also the extremes in 1855 and 1863 show a period of 9 years. 



The periodic change of the lunar perigee (8 years 310*5 days) 

 and of the inclination of the moon's orbit to the ecliptic (9 

 years 109*5 days) nearly coincides with the periodic change of 

 annual temperatures above mentioned. If the radiation of heat 

 reflected on the earth by the moon is perceptible, the amount of 

 heat received by the earth's surface must depend on the inclina- 

 tion of the lunar orbit to the ecliptic, and on the distance of the 

 moon from the earth. 



Suppose S to be the sun, M E the 

 projection of the lunar orbit in its 

 maximum of inclination, mE in its 

 minimum, /j, E in the mean position, 

 S E the projection of the ecliptic, it 

 is evident that the radiant heat will 

 be reflected by the moon in higher 



quantity in the position m E than in the mean position yu, E, and 

 in the position (maximum) ME. Hence we must suppose the 

 radiant heat will be sent to the earth on a larger scale during a 

 period of 4 years 8 months nearly, when the moon, from the mean 

 position of its orbit, approaches to the minimum of inclination, 

 than during the same time when she is approaching the maxi- 

 mum of inclination. 



The following Table contains the relative position of the node 

 &<l to the inclination of the orbit, and the average of annual 

 temperatures during the periods of 4 years 8 months : — 



