RAIXS AND En^KS. 107 



cially for the trade-wind belts of the Atlantic and the monsoon 

 region of the Indian Ocean. All the rain which the monsoons 

 of India dehver to the land the rivers of India return to the sea. 

 And if, in measuring this for the whole of India, our gauges should 

 lead us into a probable error, amounting in volume to half the dis- 

 charge of the Mississippi Kiver, it would not make a ditierence in 

 the computed rate of the effective daily evaporation from the North 

 Indian Ocean exceeding the one two-thousandth part of an inch 

 (0.002 in.). 



283. That part of the extra-tropical North Atlantic under con- 

 Hypsometiy in the sidcratiou is pcculiar as to its hypsometry. It is 



North Atlantic pe- , tit -t t-t !> 



cuiiar. traversed by large icebergs, v/hich are more lavour- 



able to the recondensation of its vapours than so many islets would 

 be. Warm waters are in the middle of it, and both the east and 

 the west mnds, which waft its vapours to the land, have, before 

 reaching the shores, to cross cmTents of cool water, as the in-shore 

 cmTent counter to the Guh' Stream on the western side, and the cool 

 drift fi'om the north on the east side. In illustration of this view, 

 and of the influence of the icebergs and cold currents of the Atlantic 

 upon the hypsometry of that ocean, it is only necessary to refer to 

 the North Pacific, where there are no icebergs nor marked contrasts 

 between the temperatm'e of its currents. Ireland and the Aleutian 

 Islands are situated between the same parallels. On the Pacific 

 islands there is an uninterrupted rain-fall during the entire winter. 

 At other seasons of the year sailors describe the weather, in their 

 log-books, there as " raining pretty much aU the time." This is 

 far h^om being the case even on the western coasts of Ireland, where 

 there is a rain-fall of only 47 * inches — probably not more than a 

 third of what Oonalaska receives. And simply for this reason : the 

 winds reach Ireland after they have been robbed (partially) of the 

 vapours by the cool temperatures of the icebergs and cold currents 

 which lie in their way ; whereas, such being absent from the North 

 Pacific, they arrive at the islands there literally reeking wiih. 

 moistm-e. Oregon in America, and France on the Bay of Biscay, 

 are between the same parallels of latitude; their situation ^vith 

 regard both to wind and sea is the same, for each has an ocean to 

 windward. Yet their annual rain-fall is, for Oregon,! 65 inches, 

 for France, 30. None of the islands which curtain the shores of 

 Europe are visited as abundantly by rains as are those in the same 

 latitudes which curtain our north-west coast. The American water- 

 * Keith Johnston. f Army Meteorological Kegister, 1855. 



