THE FIRST TRACES OF MAN IN EUROPE. 677 



to the time of the above-mentioned submergence of so much of Europe, 

 the countries mentioned were so high above the sea-level of the time 

 that the bottom not only of the Straits of Dover but of a large portion 

 of the North and Baltic Seas was dry ground. These waters have a 

 depth even now of only some 200 feet rarely of 250 feet so that an 

 elevation geologically very slight would expose the bottom of these 

 shallow seas. So Ireland was then connected with Great Britain, and 

 the latter with France; Avhile Africa and Europe were joined by 

 bridges of land, so to speak, e. g., by way of Gibraltar, and again by 

 way of Sicily and Malta. As a natural result and confirmation of the 

 latter instance, we find on these islands and the contiguous main-lands 

 the remains of mammals peculiarly African, especially certain species 

 of elephants. These strips of dry land divided the Mediterranean into 

 several inland seas. If man existed in that remote epoch, as many 

 arguments tend to prove, he could cross dry-shod between Africa and 

 Europe, as did the animals just mentioned, and was a witness of a 

 distribution of land and water in Europe and adjacent lands widely 

 different from that of our day. There was also going on about him 

 and beneath his feet the slow rising and sinking of vast continental 

 and insular territories processes requiring thousands of years for 

 their accomplishment and, if man's existence during them be admit- 

 ted, constituting another proof of the great antiquity of the race. 



It is to these slowly-effected but most important alterations in both 

 the contour and relief of the surface that we must ascribe the great 

 changes of the climate, not alone of separate localities, but of entire 

 continents ; and this conclusion we will finally use in explanation of 

 the varied phenomena of the Ice period, with which we have specially 

 to do. The Ice period, we have said; but, without attaching much 

 importance to the astronomical influences previously mentioned, we 

 are compelled to believe in a succession of Ice periods, the evidences 

 of which are believed to be furnished in the several series of deposits 

 that are assigned to corresponding epochs. 



During the latter portion of the Diluvial period the earth acquired 

 substantially the same relief as it has at present. The chief mountain- 

 ranges, the Juras, the Yosges, the Black Forest, the Pyrenees, the 

 Alps, etc., were then about what they are now, though somewhat 

 higher relatively both to the sea-level and to the subjacent plains ; for, 

 by the operation of various natural forces, peak after peak has been 

 either shattered and cast down, or slowly worn away, and their debris, 

 carried down in the form of sand, gravel, or larger masses, have grad- 

 ually but considerably raised the level of the valleys and plains. 



We now proceed to consider the several subdivisions of the Diluvial 

 and the Post-diluvial but prehistoric periods, and the traces of human 

 existence belonging to each. 



1. The Age of Mammoths. The loess, the layer of calcareous 

 loam, sand, and gravel, with which our hills are covered, is full of the 



