278 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. 



would become first brackish, and then briny. Now suppose the 

 water lasins which hold the lakes to be over a thousand fathoms, 

 (six thousand feet) deep. We know they are not more than four 

 hundred and twenty feet deep; but suppose them to be six thou- 

 sand feet deep. The process of evaporation, after the St. Law- 

 rence has gone dry, might go on until one or two thousand feet 

 or more were lost from the sm^face, and we should then have 

 another instance of the level of an island water-basin being far 

 below the sea-level, as in the case of the Dead Sea ; or it would 

 become a rainless district, when the lakes themselves would go 

 dry. Or let us take another case for illustration. Coralhnes are 

 at work about the Gulf Stream ; they have built up the Florida 

 Eeefs on one side, and the Bahama Banks on the other. Suppose 

 they should build up a dam across the Florida Pass, and obstruct 

 the GuJ.f Stream ; and that, in like manner, they were to connect 

 Cuba mth Yucatan by damming up the Yucatan Pass, so that the 

 waters of the Atlantic should cease to flow into the Gulf of Mexico. 

 "What shoidd we have ? The depth of the marine basin which 

 holds the waters of that Gulf is, in the deepest part, about a mile. 

 We should therefore have, by stopping up the channels between the 

 Gulf and the Atlantic, not a sea-level in the Gulf, but we should 

 have a mean level between evaporation and precipitation. If the 

 former were in excess, the level of the Gulf waters would sink down 

 until the surface exj)osed to the air would be just sufficient to retm^n 

 to the atmosphere, as vapour, the amount of water discharged by 

 the rivers — the Mississippi and others, into the Gulf. As the 

 waters were lowered, the extent of evaporating surface would 

 grow less and less, until Natm^e should establish the proper ratio 

 between the abihty of the air to take up and the capacity of the 

 clouds to let doTSTi. Thus we might have a sea whose level would 

 be much farther below the water-level of the ocean than is the Dead 

 Sea. 



538. There is still another process, besides the one already 

 The formation of in- alludcd to, bv which the draiuaejo of these inland 



land basins— a tlnrd ,. '/, n.i c ,^ • i i 



p^oce^s. basms may, through the agency oi the \Mnas, nave 



been cut off by the gi'eat salt seas, and that is by the elevation 

 of continents from the bottom of the sea in distant regions of the 

 earth, and the substitution caused thereby of dry land instead of 

 water for the winds to blow upon. Now suppose that a conti- 

 nent should rise up in that part of the ocean, wherever it may be^ 

 that supphes the clouds ^^ith the vapour that makes the rain for 



