674 THE POPULAR SCIENCE MONTHLY. 



Rameses. The stalagmites of the Kent Cavern, England, which cover 

 both Roman relics and palaeolithic implements of the Magdalenian 

 period, have been made the basis of calculations which give an age of 

 more than three hundred thousand years to the more ancient of the 

 deposits. This, of course, is upon the supposition that the rate of in- 

 crustation has never been more rapid than it is now. Other calcula- 

 tions are more general in their bearing. The oscillations of the Euro- 

 pean lands under which Denmark, North Germany, and Russia have 

 been raised from submergence during the Quaternary period, Scandi- 

 navia was depressed and has been slowly raised again, and England 

 has been sunk till the connection that existed between it and the con- 

 tinent during the whole Quaternary period has been destroyed, re- 

 quired not less than seventy thousand years. Still another grand and 

 surprising phenomenon, the extension of the Alpine glaciers, by which 

 huge rocks were carried to distances of seventy or one hundred and 

 seventy-five miles, required an enormous length of time. The maxi- 

 mum rate of progress of these blocks is not more than sixty metres 

 a year ; but in Quaternary times, when the slopes were not nearly so 

 steep as now, the rate was, according to M. de Mortillet, five times 

 slower, and each en*atic block must have taken more than twenty 

 thousand years to be carried from Mont Blanc to the lower Rhone. 

 We may add that an enormous number of blocks were thus trans- 

 ported to form the terminal moraine. Add to the period of exten- 

 sion the period occupied in the retreat of the same glaciers, which 

 must have been nearly as long as the other, and we shall find that 

 the one hundred thousand years which M. de Mortillet asks for to 

 express the duration of the glacial epoch is not an exaggeration. 

 The epochs of the extension and retreat of the glaciers were, how- 

 ever, preceded by a pre-glacial period, and all the calculations to- 

 gether induce M. de Mortillet to adopt a total of two hundred thou- 

 sand years to represent the entire duration of the Quaternary period, 

 during which we are assured of the presence of man on European soil. 

 This period, long as it appears, is very short as compared with the 

 myriads of ages of geological development that preceded it, and rep- 

 resents only the last and the shortest of the geological periods. The 

 question arises, How has the human race been able to spread itself over 

 the whole surface of the globe ? Is it the product of different and in- 

 dependent origins in the several continents, or have all men sprung 

 from a common cradle, a " mother-region " ? On this point students 

 are divided, Agassiz holding that men were created, and Carl Vogt 

 that they were developed, at different centers, and Quatrefages and 

 the theologians maintaining the unity of their origin. The fact is left 

 that man, the same in all the essential characteristics of the species, 

 has advanced into all the habitable parts of the globe, and that not 

 recently, and when provided with all the resources that experience and 

 inventive genius could put at his disposal, but when still young and 



