470 



PHYSICAL GEOGRAPHY. 



The amount collected at a low level is the greatest, because the drops enlarge in their 

 descent. They bring with them the low temperature of the upper regions of the atmo 

 sphere, and condense on their surfaces the vapour in the inferior and warmer strata. 



1. The average annual fall of rain is the greatest within the tropics. It decreases in 

 quantity as we recede from thence towards the poles, because heat, the cause of vapour, 

 diminishes. In the table, the amount is contrasted as observed in tropical and mean or 

 high latitudes : 



Though the amount of precipitation is thus far greater within the tropics than in the 

 temperate zone, yet the number of rainy days is less, because the fall, intense w"hile it 

 lasts, is a periodical event Two seasons divide the year wet and dry ; and during the 

 dry season, entire months frequently pass away without a shower descending, or a cloud 

 being seen. In the temperate zone, also, passing from south to north, the number of 

 rainy days increases, although the intensity of rain diminishes. The average annual 

 number of days on which rain falls at the places mentioned has been given as follows : 



But while in the east of Ireland the rainy days amount to 208 in the year, a far less 

 quantity of rain descends than is precipitated at Gibraltar in 68 days. 



North of the equator, the periodical tropical rains fall during the northern declination 

 of the sun, and commence south of the equator with its southern decimation, except in 

 India, where the wet and dry seasons are regulated by the monsoons. This is a benign 

 arrangement, offering relief from the rays of a vertical sun by the screen of cloud which 

 is coincidently expanded. In some parts of the American continent, and in the West 

 Indies, two wet seasons mark the year ; but one is of much shorter duration, and has 

 lighter showers, than the other. Two periods of rain are also mentioned in relation to Judea ; 

 the " first" or autumnal rains, which fall in seed-time, towards the close of October ; 

 and the " latter" or spring rains, in April, after the cold season. " I will give you the rain of 



