Occurrence of Flint-implements in Gravel-beds. 235 



beds they become outside of a bright opaque white or poreelainic ; 

 in white calcareous or siliceous sand their fractured black surfaces 

 remain almost unchanged ; whilst in beds of ochreous and ferru- 

 ginous sands, the flints are stained of the light yellow and deep brown 

 colours so well exhibited in the common ochreous gravel of the 

 neighbourhood of London. This change is the work of very long 

 time, and of moisture before the opening out of the beds. Now in 

 looking over the large series of dint-implements in M. de Perthes' col- 

 lection, it cannot fail to strike the most casual observer that those from 

 Mencbecourt are almost always white and bright, whilst those from 

 Moulin Quignon have a dull yellow and brown surface ; and it may be 

 noticed that whenever (as is often the case) any of the matrix adheres 

 to the flint, it is invariably of the same nature, texture, and colour 

 as that of tbe respective beds themselves. In the same way at St. 

 Acheul, where there are beds of white and others of ochreous gravel, 

 the flint-implements exhibit corresponding variations in colour and 

 adhering matrix ; added to which, as the wdiite gravel contains chalk 

 debris, there are portions of the gravel in which the flints are more 

 or less coated with a film of deposited carbonate of lime ; and so it is 

 with the flint-implements which occur in those portions of the 

 gravel. Further, the surface of many specimens is covered with fine 

 dendritic markings. Some few implements also show, like the 

 fractured flints, traces of wear, their sharp edges being blunted. In 

 fact, the flint-implements form just as much a constituent part of 

 the gravel itself — exhibiting the action of the same later influences 

 and in the same force and degree — as the rough mass of flint frag- 

 ments with which they are associated. 



With regard to the geological age of these beds, the author refers 

 them to those usually designated as post-pliocene, and notices their 

 agreement with many beds of that age in England. The Mencbe- 

 court deposit much resembles that of Fisherton near Salisbury ; the 

 gravel of St. Acheul is like some on the Sussex coast ; and that of 

 Moulin Quignon resembles the gravel at East Croydon, Wandsworth 

 Common, and many places near London. The author even sees 

 reason, from the general physical phenomena, to question whether 

 the beds of St. Acheul and Moulin Quignon may not possibly be 

 of an age one stage older than those of Mencbecourt and St. Roch ; 

 but before that point can be determined, a more extended knowledge 

 of all the organic remains of the several deposits is indispensable. 



The author next proceeds to inquire into the causes which led 

 to the rejection ot this and the cases before mentioned, and shows 

 that in the case of M. de Perthes' discovery, it was in a great degree 

 the small size and indifferent execution of the figures and the 

 introduction of many forms about which there might reasonably 

 be a difference of opinion ; — in the case of the arrow-heads in Kent's 

 Cave a hidden error was merely suspected ; — and in the case of 

 the Liege cavern he considers that the question was discussed on 

 a false issue. He therefore is of opinion that these and many similar 

 cases require reconsideration ; and that not only may some of these 

 prove true, but that many others, kept back by doubt or supposed 

 error, will be forthcoming. 



