354 



On the influence of the Moon 



[July; 



But as the heating power of the sun (as the year advances) must 

 affect the current of air, and consequently the dew-points, whereas the 

 tides of the sea are affected wholly by the attractive forces of the sun 

 and moon, no correct comparison can be drawn between them. Thus 

 the first item under " Full" is 46 - 3, which is less than the item under 

 " New," 53" 1. But it may be said, that the time of the average 

 46*3, is near 15 days earlier than that of the corresponding average 

 53" 1 ; that as the dew-points increase with the year from January to 

 June, owing to the heat principally, the item under " Full" (46"3) is 

 less than that under " New" (53 - l), owing to its being so much earlier, 

 and consequently less affected by the heat of the sun. To obviate this 

 difficulty, we may remark that, if the first item under " Full" is 15 days 

 earlier than that under " New," the next item below it (62'1) is fifteen 

 days later ; the mean between them therefore would correct any dis- 

 crepancy arising from increase or decrease of heat in either case. 



Proceeding in this manner, i. e. taking the mean of each number in 

 succession with the one below it, in the column headed " Full," the 

 comparison becomes as follows. I have placed the Bombay tides of 

 the same period in the same line, that the agreement may be more 

 apparent. 



Dew-points, Calcutta. 

 New moon. Full moon. 



531 

 54-3 



66-8 

 *74-5 

 78-1 

 77-5 

 77-6 

 77-3 

 75-3 



54-2 

 60-7 

 66-1 

 75-2 

 76-2 

 75-5 

 76-6 

 76-7 

 75-4 



*73'2 69-4 



58-8 61-9 



51-5 52-2 



Tides, in Bombay Harbour. 



New (Day). Full (Night). 



ft. 



in. 



12 



11 



13 



5 



14 



3 



*15 



3 



15 



9 



16 



5 



16 



5 



16 



1 



15 



6 



14 



11 



*14 



3 



13 



3 



ft. 



in. 



17 







16 



1 



16 







15 



4 



13 



10 



14 



1 



12 



9 



13 







13 



1 



13 



11 



15 







15 



10 



Disclaiming then the wish of speaking positively on a subject where 

 no decisive proof has been adduced, we may yet be allowed to assert, 

 as exceedingly probable, that the dew-points, upon the whole, vary 

 with the declination of the moon, and in the same manner as the tides 

 of the sea do. 



I have been induced to publish the above remarks from having seen 

 a popular notice of M. Arago's paper on lunar influence. One of the 

 firstremarks is, that the number of rainy days is increased by the moon's 

 perigee. The number of rainy days in apogee being to those in peri- 

 gee ; : 1069 : 1169. This would agree very- well with the notion of 



