674 THE POPULAR SCIENCE MONTHLY. 



deposits of loam, sand, gravel, and rocks, evidently brought from con- 

 siderable distances by some vast current that once covered the low- 

 lands, aud even lesser hills ; for, in the Rhine Valley this surface- 

 layer is found at elevations of 300 to 600 feet above the present river- 

 level. The bowlders are of various rocks that are not native to this 

 region, but are found in the Juras, the mountains of the Black Forest, 

 the Vos"es, and especially the Alps, of whose mass these constitute a 

 large proportion. A similar drift is found over the wide, rolling 

 country between the Juras and the Alps, and indeed over nearly all 

 the lowlands and valleys of Europe and the world. From the er- 

 roneous, but once universal belief, that it was produced by the Noa- 

 chian Deluge, or the all-submerging flood of which the Sagas of so 

 many nations are full, this deposit was early named the diluvium, or 

 diluvial deposit. It consists, according to this view, of the detritus 

 from mountain ranges, transported and scattered -broadcast over lower 

 levels by the Deluge. 



This latest of geological formations rests upon the upper strata of 

 the Tertiary, when they are present, In the Pvhine Valley, however, 

 it covers the Miocene or middle Tertiary ; and in other regions, the 

 chalk, the Jurassic, or even older formations. Upon the diluvium it- 

 self are built most of our cities, and in it will most of us be buried. 

 The melted snows, the rains, and the waters of our streams, penetrate 

 through its loose layers until the more impervious underlying clays 

 (mostly Tertiary) arrest and hold them in readiness to supply our 

 daily needs. The diluvium seldom yields much that is of mineral or 

 industrial value, except the material of our tiles, brick, and mortar. 

 In California, Brazil, Australia, and the Ural Mountains, however, its 

 gravels are rich in gold, platinum, and jewels of various sorts, and in 

 some localities tin-ores are found in it. 



Geologists have been long occupied with the study of the producing 

 causes of those vast floods, the effects of which are so strikingly seen 

 in the pebbly plains and terraces of our river-valleys, and in the layers 

 of sand and loam upon our uplands and hills. That there once were 

 there masses of flowing water-currents, like, yet far vaster than, our 

 present rivers, cannot be intelligently doubted. The absence of marine 

 shells and the universal abundance of the remains of land-animals in 

 the deposits in discussion forbid the belief that the sea covered our 

 own and the adjacent continents during this latest of geological eras. 



All the hypotheses advanced in explanation of the phenomena we 

 have mentioned cannot be here adduced ; we can only say that the 

 great majority of recent geologists agree and assert that these im- 

 mense streams were chiefly produced by the melting of snows and 

 glaciers, that must then have extended not merely from the Alps and 

 Pyrenees, as at present, but from the north, southward over a large 

 portion of Europe ; even the smaller ranges, such as the Vosges and 

 Black Forest, then having each its glacier system. 



