POST-PLIOCENE ALLUVIUM. 93 



CHAPTER VI. 



POST-PLIOCENE ALLUVIUM AND CAVE DEPOSITS WITH 

 FLINT IMPLEMENTS. 



GENERAL POSITION OF DRIFT WITH EXTINCT MAMMALIA IN VALLEYS 



DISCOVERIES OF M. BOUCHER DE PERTHES AT ABBEVILLE FLINT 



IMPLEMENTS FOUND ALSO AT ST. ACHEUL, NEAR AMIENS CURIOSITY 



AWAKENED BY THE SYSTEMATIC EXPLORATION OF THE BRIXHAM CAVE 



FLINT KNIVES IN SAME, WITH BONES OF EXTINCT MAMMALIA SUPER- 

 POSITION OF DEPOSITS IN THE CAVE VISITS OF ENGLISH AND FRENCH 



GEOLOGISTS TO ABBEVILLE AND AMIENS. 



Post-pliocene Alluvium containing Flint Implements in the 

 Valley of the Somme. 



mHEOUGHOUT a large part of Europe we find at mode- 

 -*- rate elevations above the present river-channels, usually 

 at a height of less than forty feet, but sometimes much 

 higher, beds of gravel, sand, and loam containing bones of 

 the elephant, rhinoceros, horse, ox, and other quadrupeds, 

 some of extinct, others of living, species, belonging for the 

 most part to the fauna already alluded to in the last chapter 

 as characteristic of the interior of caverns. The greater part 

 of these deposits contain fluviatile shells, and have un- 

 doubtedly been accumulated in ancient river-beds. These 

 old channels have long since been dry, the streams which 

 once flowed in them having shifted their position, deej)ening 

 the valleys, and often widening them on one side. 



It has naturally been asked, if man coexisted with the 

 extinct species of the caves, why were his remains and the 

 works of his hands never imbedded outside the caves in 

 ancient river-gravel containing the same fossil fauna ? AVhy 

 should it be necessary for the geologist to resort for evidence 



