THE FIRST TRACES OF MAY IN EUROPE. 675 



Strongly in favor of this view are the erratic bowlders and blocks 

 of stone, and the heaps and ridges of drift, so widely scattered over the 

 mountains, plains, and valleys of Europe and North America, precisely 

 similar as they are to those left by the retreat of the glaciers at the 

 present time. And then, as now happens, the melting of floating ice- 

 bergs, that were detached from the foot of glaciers as they reached the 

 coast, strewed the ocean-bed with stones, gravel, and mud. The wide 

 plains of Northern Germany are abundant in rocks and gravel from 

 Scandinavia and Finland, for example. Our surface-deposits, there- 

 fore, are simply the detritus and debris of mountain-regions, trans- 

 ported thence by glaciers, and spread over our lower levels by the 

 rivers that the melting of these glaciers produced. 



This theory was first definitely propounded by Venetz, and ha* 

 since been developed and verified by Charpentier, Agassiz, Forbes, 

 and many others. Many geologists have opposed it from the first, 

 but it may now be regarded as of practically universal acceptance, and 

 as crainin"- constant confirmation from the immense number of facts 

 annually observed and published. 



The glacial theory implies the former prevalence in Europe and 

 North America of a climate marked by much snow and rain, as well 

 as ice ; and this is confirmed by the characteristics of the fauna and 

 flora of the time. 1 In addition to the waters produced by the melting 

 of glacial masses then covering so large a portion of the Northern 

 Hemisphere, the very great rainfall incident to such a climate would 

 swell the volume of the great currents of the period currents not of 

 transient flow like mere mountain-torrents, or our local freshets, but 

 that swept on for centuries or millenniums. Minor additional inunda- 

 tions, also, would result from risings and subsidences of the earth's 

 surface in given localities, from the damming of the waters in the val- 

 leys by glaciers and avalanches, from the sudden emptying of moun- 

 tain-lakes thus formed, and possibly from earthquakes. It is to these 

 various causes that we may attribute the washing out of the lower ter- 

 races of our present river-valleys. 



The great currents by which we explain the various phenomena of 

 the drift are due to the glaciers of this Ice period, then ; and this sug- 

 gests the further question, What produced the Ice period itself, the 

 long-prevailing low temperature of regions now warm or temperate ? 

 A vast array of observations commends to the attention the following 

 answer : 



There was then a distribution of land and water upon the earth 

 very different from the present, and, as the result of it, a different sys- 

 tem and direction to the currents of the sea and air. And there are 



1 Prof. Oswald Heer has given, in his " Urwelt der Schweiz," a description, at once 

 scientific and entertaining, of the Swiss fauna and flora of the Drift period. In his valu- 

 able studies upon the diluvial flora, Count Gaston de Saporta concludes in favor of a 

 climate in this period marked rather by extreme moisture than by extreme cold. 



