THE GEOLOGICAL AGENCY OF THE WINDS. 287 



basin of tlio Dead Sea, in the basin of the Caspian, of the Sea of 

 Aral, and in the other inland basins of Asia, we are entitled to 

 infer that the j)recipitation and evaporation are at this time 

 exactly equal. Were it not so, the level of these seas would 

 be rising or sinking. If the precipitation were in excess, these 

 seas w^ould be gradually becoming fuller ; and if the evaporation 

 were in excess, they w^ould be gradually drj'ing up ; but observa- 

 tion does not show, nor history tell us, that either is the case. 

 As far as w'e know, the level of these seas is as permanent as 

 that of the ocean, and it is difficult to realize the existence of 

 subterranean channels between them and the great ocean. Were 

 there sach a channel, the Dead Sea being the lower, it would be 

 the recipient of ocean waters ; and we cannot conceive how it 

 should be such a recipient without ultimately rising to the level 

 of its feeder. 



535. WJience come its rains f — It may be that the question 

 suggested by m}^ researches has no bearing upon the Dead Sea ; 

 that local elevations and subsidences alone were concerned in 

 placing the level of its waters where it is. But is it probable 

 that throughout all the geological periods, during all the changes 

 that have taken place in the distribution of land and water 

 surface over the earth, the winds, which in the general channels 

 of circulation pass over the Dead Sea, have alone been un- 

 changed ? Throughout all ages, periods, and formations, is it 

 probable that the winds have brought us just as much moisture 

 to that sea as they now bring, and have just taken up as much 

 water from it as the}'- now carry off? Obviously and clearly not. 

 The salt-beds, the water-marks, the geological formations, and 

 other faets traced by Nature's own hand upon the tablets of the 

 rock, all indicate plainly enough that not only the Dead Sea, but 

 the Caspian also, had upon them, in foimer periods, more abundant 

 rains than they now have. Where did the vapour for those rains 

 come from ? and what has stopped the supply ? Surely not the 

 elevation or depression of the Dead Sea basin. My researches 

 with regard to the wdnds have suggested the probability (§ 290) 

 that the vapour which is condensed into rains for the lake valley, 

 and which the St. Lawrence carries off to the Atlantic Ocean, is 

 taken up by the south-east trade winds of the Pacific Ocean. 

 Suppose this to be the case, and that the winds which bring this 

 vapour anive with it in the lake country at a mean dew-point of 

 50°. Let us also admit the south-west winds to be the rain 



