LECTURE X. 283 



and tlie form of the ground surface became what it is now ; 

 though in these newly scooped out valleys numerous other 

 geological processes took place, the investigation of which has 

 scarcely commenced, but which, unquestionably, assign this 

 final excavation to a very remote period, 



" The grey and red diluvium are found with all their cha- 

 racteristics at St. Acheul, Menchecourt, and in many other 

 places of the Somme valley ; loess also occurs there, but in a 

 very rudimentary form. 



" The numerous flint-hatchets which testify to the existence 

 of man in the beginning of the quaternary period, have been 

 found in the grey diluvium, which is covered by its double 

 undisturbed mantle. 



" This deposit of Moulin- Quignon shows neither the cha- 

 racters of the grey nor of the red diluvium, but seems to 

 be the result of a mixture of both, produced by disturbed 

 waters ; perhaps, by the same waters which scooped out the 

 valleys. 



" The last excavation was, perhaps, not a simple phenome- 

 non ; for the deposit of Moulin- Quignon is, as has been shown, 

 intersected by vertical, natural shafts, resembling those pro- 

 duced by the red diluvium ; but differing so far that the latter, 

 as seen at St. Acheul and Paris, are filled with the red dilu- 

 vium, whilst those of Moulin-Quignon are filled with a mani- 

 festly more recent clayish matter, resembling vegetable soil. 

 This is, perhaps, an indication of a seventh phase in the quater- 

 nary period. 



" The formation of the peat deposits must, in my opinion, be 

 placed in an epoch subsequent to the above periods. 



" In conclusion, I would just observe that the natural shafts, 

 which intersect the gravel brook of Moulin-Quignon, can no 

 ways be considered as having favoured the introduction of the 

 jaw in question to the bottom of the deposits." 



" The jaw was situate in a bed of black flint, perfectly dis- 

 tinct from the shafts, and the ferruginous substance had 

 filtered through a fissure which pervades the whole mass from 

 the surface down to the bottom, and which was itself filled 

 with the same ferruginous mass, which it had carried down at 



