STRATIGRAPHICAL GEOLOGY. 541 



It is impossible to enter in detail into the important results 

 of modern investigation of diluvial deposits, the more general 

 aspects have been fully treated in a previous chapter (cf. pp. 

 220-239). Many of the questions are subjects of controversy at 

 the present time, such as the origin of the Loess deposits, the 

 number of distinct Ice Ages, the geographical distribution of 

 glacial formations, and the age and significance of the various 

 pebble, sand, and clay formations. Curiously enough, the 

 youngest of the geological formations was the last to be 

 generally understood, and its scientific investigation is a 

 conspicuous feature of the present phase of progress in 

 geology. 



The question of the age of the human race, and the environ- 

 ment of early man, brings geology into the closest relationship 

 with anthropology, and for the last four decades geology 

 has done what it could to assist in the solution of the great 

 problems associated with the beginnings of human life upon 

 the earth's surface. 



