302 THE PHYSICAL GEOGRAPHY OF THE SEA. 



entitled to regard (§ 542) the Mediterranean, the Eed Sea, and 

 Persian Gulf as relays, distributed along the route of these thirsty 

 winds from the continents of the other hemisphere, to supply them 

 with vapors, or to restore to them that which they have left be- 

 hind to feed the sources of the Amazon, the Niger, and the Congo. 



553. The hypothesis that the winds from South Africa and 

 Hypothesis support- AmcHca do take the course through Europe and 

 ed by facts. Asia which I havc marked out for them (Plate 

 YII.), is supported by so many coincidences, to say the least, that 

 we are entitled to regard it as probably correct, until a train of 

 coincidences at least as striking can be adduced to show that such 

 is not the case. Keturning once more to a consideration of the 

 geological agency of the winds in accounting for the depression 

 of the Dead Sea, we now see the fact palpably brought out before 

 us, that if the Straits of Gibraltar were to be barred up, so that no 

 water could pass through them, we should have a great depression 

 of water-level in the Mediterranean. Three times as much water 

 (§ 547) is evaporated from that sea as is returned to it through 

 the rivers. A portion of water evaporated from it is probably 

 rained down and returned to it through the rivers; but, suppos- 

 ing it to be barred up: as the demand upon it for vapor would 

 exceed the supply by rains and rivers, it would commence to dry 

 up ; as it sinks down, the area exposed for evaporation would de- 

 crease, and the supplies to the rivers would diminish, until finally 

 there would be established between the evaporation and precipi- 

 tation an equilibrium, as in the Dead and Caspian Seas. But, for 

 aught we know, the water-level of the Mediterranean might, be- 

 fore this equilibrium were attained, have to reach a stage far be- 

 low that of the Dead Sea level. The Lake Tadjura is now in the 

 act of attaining such an equilibrium. There are connected with 

 it the remains of a channel by which the water ran into the sea ; 

 but the surface of the lake is now five hundred feet below the 

 sea-level, and it is salting up. If not in the Dead Sea, do we not, 

 in the valley of this lake, find outcropping some reason for the 

 question. What have the winds had to do with- the phenomena 

 before us ? 



554. The winds, in this sense, are geological agents of great 

 power. It is not impossible but that they may afford us the 

 means of comparing, directly, geological events which have taken 



