264 ANNUAL OF SCIENTIFIC DISCOVERY. 



counting for the formation of this or that inland basin, is worthy, afc 

 least, of consideration. Is there any evidence that the annual amount 



/ 



of precipitation upon the water-shed of the Dead Sea, at some former 

 period, was greater than the annual amount of evaporation ? If yea, 

 where did the vapor that supplied that precipitation come from, and 

 what has cut off that supply ? The mere depression of the lake-bed 

 would not do it. If there were ever a river from the Dead Sea to the 

 arms of the ocean about it, we may imagine that river to have abounded 

 with falls, as the rivers do which drain the lakes into the Atlantic. 

 And if we establish the fact that the Dead Sea did ever send a river to 

 the ocean, we carry along with it the admission, that when that sea over- 

 flowed into that river, then the water that fell from the clouds over the 

 Dead Sea basin was more than the winds could convert into vapor and 

 carry away again. In the basin of the 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 precipitation and evaporation are at this 

 time exactly equal ; were it not so, the level of these seas would be 

 rising or sinking. As far as we know, the level of these seas is as per- 

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

 of subterranean channels between it and the great ocean. Were there 

 such a channel, the Dead Sea being 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. It may 

 perhaps be evident that the question suggested by my 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 which 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 unchanged ? 



Where does the water which falls from the clouds upon the valley of 

 the great North American Lakes come from 1 It goes into the sea, 

 and out of the sea it must come again ; else " the sea would be full." 

 From what part of the sea, therefore, do the clouds get vapor to make 

 rain of for the lake country ? 



The researches conducted at the National Observatory, with regard 

 to the winds, have suggested the probability that the vapor which is 

 condensed into rains for the lake valley, and the excess of which the 

 St. Lawrence carries off to the Atlantic, is evaporated by the S. E. trade 

 winds of the Pacific. Suppose this to be the case, and that the winds 

 which bring this vapor arrive with it in the lake country at a mean dew 

 point of 50. This would make the S. W. winds the rain winds for 

 the lakes, generally, as well as for the Mississippi valley. They are 

 also, speaking generally, the rain winds of Europe ; and, I have no 

 doubt, of extra-tropical Asia, also. Now, suppose a certain mountain- 

 range, thousands of miles to the S. W. of the lakes, but across the path 

 of these winds, were to be suddenly elevated, and its crest pushed up 

 into the regions of snow, having a mean temperature of 30 F. Now 

 the winds, in passing that range, would be subjected to a dew point of 

 30 ; and, not meeting with any more evaporating surface between such 



