PNEUMATICS. 73 



of rain and dew is probably from 35 to 40 inches, it 

 is obvious that the supply of atmospheric moisture 

 must be renewed many times in the course of a year. 



Rain. 



Nature has so arranged it, that the supply of the 

 atmospheric moisture is most abundant in the lati- 

 tudes where the evaporation is most rapid ; or rather 

 the processes of evaporation, depending partly on the 

 same principles and exerting a reciprocal influence, 

 tend to adjust themselves to each other, although 

 this tendency is perpetually disturbed by local 

 causes.* 



The result of experiment has shown that a greater 

 amount of rain falls while the sun is below, than 

 while it is above the horizon. 



Rain. 



The mean quantity of rain is greatest at the equa- 

 tor, and decreases as the poles are approached. 



Inches. 



At Grenada, in 12 N. lat. it is per annum 126 

 Cape Francais 19-46 ditto 120 



Calcutta 22-23 ditto 81 



Rome 41-54 ditto 39 



England 53 ditto 32 



Petersburgh 59-16 ditto 16 



Rain at Oxford. 

 The mean quantity of rain that fell at Oxford, 



* At Lima, (lat. 12 S. long. 76 W.) situated 580 feet above 

 the level of the sea, wilhin 5 miles of the Pacific, and 20 leagues 

 of the great chain of the Andes, up to A. D. 1821, no rain had 

 fallen lor 14 years. 



