230 SUPERFICIAL TRACES OF THE EFFECTS CHAP. XIII. 



now extinct, was brought about during this concluding phase 

 of the glacial epoch. 



Although it may be impossible in the present state of our 

 knowledge to come to a positive conclusion on this head, I 

 know of no inquiry better fitted to clear up our views respec 

 ting the geological state of the northern hemisphere at the 

 time when the fabricators of the flint implements of the 

 Amiens type flourished. I shall therefore now proceed to 

 consider the chronological relations of that ancient people 

 with the final retreat of the glaciers from the mountains of 

 Scandinavia, Scotland, Wales, and Switzerland. 



Superficial Markings and Deposits left by Glaciers and 



Icebergs. 



In order fully to discuss this question, I must begin by re 

 ferring to some of the newest theoretical opinions entertained 

 on the glacial question. When treating of this subject in the 

 'Principles of Geology,' ch. xv., and in the ' Manual (or Ele 

 ments) of Greology,' ch. xi., I have stated that the whole mass 

 of the ice in a glacier is in constant motion, and that the 

 blocks of stone detached from boundary precipices, and the 

 mud and sand swept down by avalanches of snow, or by rain 

 from the surrounding heights, are lodged upon the surface 

 and slowly borne along in lengthened mounds, called in 

 Switzerland moraines. These accumulations of rocky frag 

 ments and detrital matter are left at the termination of the 

 glacier, where it melts in a confused heap called the ' terminal 

 moraine,' which is unstratified, because all the blocks, large 

 and small, as well as the sand and the finest mud, are carried 

 to equal distances and quietly deposited in a confused mass 

 without being subjected to the sorting power of running 

 water, which would convey the finer materials farther than 

 the coarser ones, and would produce, as the strength of the 



