THE GEOLOGICAL AGENCY OF THE WINDS. 283 



of the winds wliich brought the rain for the Caspian water-shed, 

 might have been sufficient to rob them of the moistm^e which they 

 were wont to carry away and precipitate upon this gTeat inland 

 basin. See how the Andes have made Atacama a desert, and of 

 Western Peru a rainless country : these regions have been made 

 rainless sunply by the rising up of a mountain range between 

 them and the vapour-springs in the ocean which feed -^ith moisture 

 the A^dnds that blow over those now rainless regions. 



544. That part of Asia, then, which is mider the lee of southern 

 peTtl'zonlVnhS'"' *^^^6-Tsd^^^ AfHca, hes to the north of the tropic 

 hemisphere that are of Caucor, aud botweon two liuos, the ono passing 

 in the trade-wind re- through Capo Palmas and Medina, the other through 

 Srir^Voun'triS Aden and Delhi. Bebg extended to the equator, 

 they will include that part of it which is crossed by the conti- 

 nental south-east trade-Tsinds of Africa after they have traversed 

 the greatest extent of land sm^face (Plate YII.). The range which 

 lies between the two lines which represent the course of the Ameri- 

 can winds mth then* vapours, and the two lines which represent 

 the com'se of the African winds with theu' vapom's, is the range 

 which is under the lee of ^N-inds that have, for the most part, tra- 

 versed water smiace or the ocean in then' cncuit as south-east trade- 

 wdnds. But a bare inspection of Plate YII. wiU show that the 

 south-east trade-winds which cross the equator between longitude 

 15° and 50° west, and which are supposed to blow over into this 

 hemisphere between these two ranges, have traversed land as well 

 as Avater ; and the Trade-Aviud Chart * shows that it is precisely 

 those ANinds which, in the summer and faU, are converted into 

 south-west monsoons for supplying the whole extent of Guinea 

 with^rains to make rivers of. Those winds, therefore, it would 

 jseem, leave much of their moisture beliind them, and pass along 

 to their channels in the grand system of cnculation, for the most 

 part, as dry A\inds. Moreover, it is not to be supposed that 

 the channels through which the winds blow that cross the 

 equator at the several places named are as sharply defined in 

 natm^e as the hues suggested, or as Plate YII. would represent them 

 to be. 



545. The whole region of the extra-tropical Old World that is 

 Their situation, and included AATitliin the ran^-es marked is the region 



trie r[in"'e ot dry ^ o o 



T%mds. ° which has most land to windward of it in the southern 



hemisphere. Kow it is a curious coincidence, at least, that all 



* Series of Maiirv's Wind and Current Charts. 



