ON THE GEOLOGICAL AGENCY OF THE WINDS. 233 



the atmosphere ; as far as our knowledge extends, the level of each 

 of these two seas is as permanent as that of the great ocean itself. 

 Therefore, the volume of water discharged bj rivers, the rains, and 

 the dews, into these two seas, is exactly equal to the volume which 

 these two seas give back as vapor to the atmosphere. 



650. These winds, therefore, do not begin permanently to lay 

 down their load of moisture, be it great or small, until they cross 

 the Oural Mountains. On the steppes of Issam, after they have 

 supplied the Amazon and the other great equatorial rivers of the 

 south, we find them first beginning to lay down more moisture 

 than they take up again. In the Obi, the Yenesi, and the Lena, 

 is to be found the volume which contains the expression for the 

 load of water which these winds have brought from the southern 

 hemisphere, from the Mediterranean, and the E,ed Sea; for in 

 these almost hyperborean river-basins do we find the first instance 

 in which, throughout the entire range assigned these winds, they 

 have, after supplying the Amazon, &c., left more water behind 

 them than they have taken up again and carried ofi^ The low 

 temperatures of Siberian Asia are quite sufficient to extract from 

 these winds the remnants of vapor which the cool mountain-tops 

 and mighty rivers of the southern hemisphere have left in them. 



651. Here I may be permitted to pause, that I may call atten- 

 tion to another remarkable coincidence, and admire the marks of 

 design, the beautiful and exquisite adjustments that we see here 

 provided, to insure the perfect workings of the great aqueous and 

 atmospherical machine. This coincidence — may I not call it cause 

 and effect? — is between the hygrometrical conditions of all the 

 countries within, and the hygrometrical conditions of all the coun- 

 tries without, the range included within the lines which I have 

 drawn (Plate VII.) to represent the route in the northern hemi- 

 sphere of the southeast trade-winds after they have blown their 

 course over the land in South Africa and America. Both to the 

 right and left of this range are countries included between the 

 same parallels in which it is, yet these countries all receive more 

 water from the atmosphere than they give back to it again ; they 

 all have rivers running into the sea. On the one hand, there is 

 in Europe the Ehine, the Elbe, and all the great rivers that empty 



