THE GEOLOGICAL AGENCY OF THE WINDS. 293 • 



trade-winds of South Africa and America — that these countries, 

 over w^hich theoiy makes these winds to blow, inchide all the 

 great deserts of Asia, and the districts of least precipitation in 

 Europe. A line from the Galapagos Islands through Florence in 

 Italy, another from the mouth of the Amazon through Aleppo in 

 Holy Land (Plate VII.), would, after passing the tropic of Cancer, 

 mark uiDon the surface of the earth the route of these winds ; 

 this is that " lee country " (§ 298) which, if such be the system 

 of atmospherical circulation, ought to be scantil}^ supplied with 

 rains. Now the hj^etographic map of Europe, in Johnston's 

 beautiful Physical Atlas, places the region of least precipitation 

 between these two lines (Plate YII.). 



542. Belays for supplying them icith vapour hy the way. — It would 

 seem that Nature, as if to reclaim this "lee" land from the 

 desert, had stationed by the wayside of these winds a succession 

 of inland seas to serve them as relays for suppljnng them with 

 moisture. There is the Mediterranean, with its arms, the Caspian 

 Sea and the Sea of xVral, all of which are situated exactly in this 

 direction, as though these sheets of water w^ere designed, in the 

 grand system of aqueous arrangements, to supply with fresh 

 vapour winds that had alieady left rain enough behind them to 

 make an Amazon and an Orinoco of. Now that there has been 

 such an elevation of land out of the water, Ave infer from the fact 

 that the Andes were once covered by the sea, for their tops are 

 now crowned with the remains of marine animals. When they 

 and their continent w^ere submerged — admitting that Europe in 

 general outline was then as it now is — it cannot be supposed, if 

 the circulation of vapour were then such as it is supposed now to 

 be, that the climates of that part of the Old ^^'orld which is under 

 the lee of those mountains were then as scantily supplied with 

 moisture as they now are. When the sea covered South America, 

 nearly all the vapour which is now precipitated upon the 

 Amazonian water-shed was convej'cd thence by the winds, and 

 distributed, it may be supposed, among the countries situated 

 along the route (Plate VII.) ascribed to them. 



543. Adjustments in this hygrometry of Caspians. — If ever the 

 Caspian Sea exposed a larger surface for evaporation than it 

 now does — and no doubt it did; if the precipitation in that 

 valley ever exceeded the evaporation from it, as it does in all 

 valleys drained into the open sea, then there must have been 

 a change of hygrometrical conditions there. And admitting the 



