go On Similarities in the 



towards the west due to the changing peripheral velocity 

 with changing latitude. Where these winds meet, there is 

 the equatorial belt of calms and rains. The regularity of these 

 conditions is disturbed by the fact above mentioned, that 

 where we have land the sun's rays raise its surface to a higher 

 temperature than in the case of their falling upon sea. The 

 consequence of this is that the air draws in towards these 

 highly heated areas, and modifies the primary trade wind, 

 producing the secondary phenomenon of monsoons. As land 

 predominates in the northern hemisphere and water in the 

 southern, these phenomena are more evident in the northern 

 than in the southern hemisphere, and they are particularly 

 evident in the Indian Ocean. The trade winds during the whole 

 of their course are travelling from regions of lower temperature 

 to those of higher temperature; hence, even though they were 

 saturated with moisture at the beginning, they would, as they 

 continued their course and their temperature rose, increase 

 their capacity for taking up moisture. Hence their great 

 characteristic quality they are drying winds 1 . 



The south-east trade wind passes chiefly over water, the 

 north-east trade blows almost equally over land and over 

 water. Its effects on land are principally visible in its progress 

 over Western Asia and Africa. From Siberia to Morocco we have 

 winds mainly from the north. Their actual direction is sometimes 

 to the eastward, sometimes to the westward of north, according 

 to the preponderance of local influences. They are of a highly 

 drying character, and this is put clearly in evidence by the chain 

 of inland drainage areas and absolute deserts which occupy this 

 broad belt of continent. Thus we have the desert of Gobi, the 

 inland basins of the Aral and the Caspian, the salt lakes of Asia 

 Minor, and the deserts of Arabia and North Africa. 



The drying power of the wind is also shown by the fact 

 that the Mediterranean, which lies in its course, but receives 

 the drainage of quite half of Europe which lies in the rainy 

 regions of the south-west winds, and that of a considerable portion 

 of Equatorial Africa by the Nile, is essentially the receptacle of 

 an inland drainage area, quite as much as the Caspian is. 

 1 See Contents, p. xvii. 



