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SCIENCE 



[N. S. Vol. XXIX. No. 739 



the North Atlantic Ocean. But we must 

 not forget that the missing link between 

 both ends of these supposed mountain 

 chains is longer than their known extent. 



There are also similar structural features 

 between the Mediterranean Sea and the 

 Gulf of Mexico and its surroundings. 

 Both seas consist of a set of very deep 

 basins, separated by higher regions which 

 reach more or less above the sea-level, and 

 the Mesozoie strata in their vicinity are 

 folded, but there is one very marked geo- 

 graphical difference between their sur- 

 roundings. On the north side of the Medi- 

 terranean Sea extends a nearly uninter- 

 rupted belt of mountains which contains 

 the highest elevation of Europe, while there 

 is no high mountain range at all at the 

 north of the Gulf of Mexico. The high 

 elevations on the north side of the Mediter- 

 ranean sharply divide western Europe into 

 an Atlantic and a Mediterranean part, 

 while all the natural regions of eastern 

 North America continue uninterrupted to 

 the Gulf. The high mountain belt on the 

 north side of the Mediterranean Sea pre- 

 vents the rivers from entering the Mediter- 

 ranean ; it pushes aside the Danube and 

 only the east annex of the Mediterranean— 

 the Black Sea— receives in the Danube, the 

 Dneiper and the Don, important rivers 

 which can be compared with the branches 

 of the Mississippi River. But the river of 

 Europe which as to size and ramifications 

 bears most resemblance to the Mississippi 

 —the Volga— empties its waters into the 

 Caspian Lake. This, the largest lake on 

 the earth, can be regarded, however, as an 

 isolated basin of the Mediterranean. Dur- 

 ing the Ice Age its waters stood probably 

 so high that they could overflow through 

 the Manytsh Valley, north of the Caucasus, 

 into the Black Sea so that the Volga got an 

 outlet into the open sea. Therefore, during 

 the Ice Age the arrangement of the eastern 

 European rivers corresponded more nearly 



with that of the Mississippi and its branch- 

 es, and this similarity would even exist if 

 we assume that then the Black Sea itself 

 was an inland sea, for such an inland sea 

 could pour its waters through the Bosporus 

 into the Mediterranean. The Bosporus, 

 indeed, bears many features of a river val- 

 ley, and it may have been at one time the 

 outlet of all European rivers from the 

 Danube to the Volga, of a body of water 

 as large as that of the Mississippi. But 

 while the large American river enters the 

 sea through a large delta deposited by it, 

 the European Mississippi passed through 

 narrows just above its mouth, as the Hud- 

 son does; it had to force its way through 

 the mountain belt north of the Mediter- 

 ranean. 



The absence of such a mountain belt in 

 North America causes an important dif- 

 ference in the climate of the peninsular 

 regions on both sides of the Atlantic. The 

 climate of Europe is hardly at all affected 

 by the Mediterranean, whereas the absence 

 of a mountain belt north of the Gulf of Mex- 

 ico allows the winds to sweep aroimd the 

 west end of that zone of high atmospheric 

 pressure which extends across the Atlantic. 

 Thus we have southwestern winds in North 

 America ; and as the southwestern winds of 

 Europe bring the moisture and the warmth 

 of the Gulf Stream drifts over large areas 

 of Europe, so also the moisture and 

 warmth of the Gulf of Mexico is brought 

 into the southeastern part of North Amer- 

 ica. The effect of the cooling influences 

 which the interior of a continent can exert 

 by its high pressure and cold on the mean 

 latitudes of its east coast, is counteracted 

 to a large extent, and peninsular North 

 America enjoys as well, but not as much, 

 as the European peninsula of Eurasia, a 

 peninsular climate. 



But the peninsular climate of both sides 

 of the Atlantic is not the same. It is most 

 strongly developed in peninsular North 



