DISTRIBUTION OF RAINS. 135 



moiintain about 5000 feet in lieigbt. At the base of that mountain 

 the annual rainfall is one hundred and twenty-seven inches. On 

 its summit there falls annually two hundred and ninety-two 

 inches. We ordinarily say that this difference is due to the fact 

 that the mountain acts as a condenser, but in the sense in which 

 we ordinarily understand that a mountain acts as a condenser, this 

 is not the case. Were the sides of that mountain of molten lava, 

 the difference between the rainfall at the base and at the summit 

 would be greater than it now is ; were its sides of lava, when 

 vapor-charged clouds should roll up its slopes, their temperature 

 would be increased, and hence their capacity for moisture be in- 

 creased ; and since the capacity for moisture increases more 

 rapidly than does the temperature, instead of pouring down rain 

 at the base, no precipitation would follow, but they would ascend 

 until they should come into a stratum of cold air, in which con- 

 densation would ensue, and then the large amount of moisture 

 secured by their high temperature would be thrown down. The 

 difference therefore, between the quantity at the base and at the 

 summit would be greater, were the sides of the mountain molten 

 lava, than would be the diflerence from their present condition. 

 It is the cold of elevation that produces condensation of moisture 

 and causes precipitation of rain, and not the mountain, in the 

 sense in which we ordinarily understand mountains to act as con- 

 densers. It is undoubtedly true that the coldness of a mountain 

 does serve to condense ; but were the mountain warm the conden- 

 sation would be greater when the clouds should have passed up 

 into that stratum of air where the necessary chilling efiect would 

 be produced. 



On the western coast of Hindostan is a range of mountains, at 

 the top of which, near Bombay, there fall annually seventy-eight 

 inches of rain. Forty-five hundred feet up the sides of the moun- 

 tain the annual rainfall is two hundred and fifty-four inches — the 

 large difference resulting principally from the cold of elevation. 

 Just over the other side of the mountain, the amount is but 

 twenty-three inches. The cause of this marked difference will be 

 noticed before the conclusion of the lecture. 



The largest amount of rainfall at any single point on the globe, 

 is probably in the southern part of the Himalaya Mountains, about 

 3000 miles north of Calcutta. There, at an elevation of 4500 feet, 

 are poured down annually six hundred and ten inches of rain. 

 You have observed, undoubtedly, from what has been stated, that 



