676 THE POPULAR SCIENCE MONTHLY. 



influences by which the climate of a given region is vastly controlled ; 

 that is, it is to the warmth of the waters of the Gulf Stream that the 

 present mildness of the climate of the, islands and coast-countries of 

 Northern Europe is owing. 



Adhemar has not been without followers, indeed, in the attempt to 

 prove that the low temperature of the Ice period was due to astronomi- 

 cal rather than terrestrial causes namely, to the change, in periods 

 of 21,000 years, of the obliquity of the earth's axis to its orbit, and the 

 still slower change in the eccentricity of that orbit itself. From the 

 cooperation of these two causes, it is said the winters of either hemi- 

 sphere would become longer and the summers shorter, and vice versa / 

 and so on, in alternate periods. For example, the earth's axis reached 

 the position most favorable to the climate of the Northern Hemisphere 

 in a. d. 1248, since which time we have been advancing toward a new 

 Ice period; whereas, antarctic regions then passed the point of great- 

 est intensity of cold. Even the relative distribution of land and sea, 

 it is affirmed, would be changed by these alternating accumulations 

 and diminutions at either pole. To all this, we can here merely reply 

 that if these astronomical facts have any influence whatever upon the 

 earth's climate, we are wholly ignorant as to its amount; and since 

 Herschel's time astronomers have been disinclined to ascribe to them 

 any considerable share in the production of climatic variations. 1 



But there is abundant evidence that during the Drift period there 

 took place extensive and considerable elevations and subsidences of 

 the earth's surface. Such elevations are still going on, as witness the 

 rise of the coast-terraces of Scotland, Sweden, Norway, Sardinia, 

 Sicily, and other lands, to a height far above the present sea-level. 

 Confusion here is easy, however, and it must not be forgotten that the 

 retreat of the shore-line would be apparently and practically an emer- 

 gence of the land, although the latter remained fixed all the time ; and 

 curiously, apparent encroachments of the sea upon the shore may be 

 an actual subsidence of the shore itself. 



A study of the drift deposits, and the organic remains found therein, 

 compels the belief that at one part of that period the lowlands of Eu- 

 rope i. e., Holland, the plains of Northern Germany, and parts of 

 Russia, Great Britain, Denmark, Sweden, and Norway were covered 

 by the North and Baltic Seas, which, thus united and enlarged, ex- 

 tended southward through Russia and Siberia, and possibly connected 

 the Black and Caspian Seas. The Desert of Sahara was also under 

 water, as Desor and Escher show. The shells of marine species yet 

 mostly extant, now found in the extensive lowlands of North America, 

 show these also to have been submerged. 



In an earlier epoch of the Diluvial period, however, that is, previous 



1 The scientific reader need not be informed that though Adhemar i9 not followed as to 

 all details, many of the best modern (especially English) scientists agree in ascribing a prom- 

 inent influence to these astronomical factors in the production of climate. Translator. 



