456 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



account of convenience of access or better materials. And instead 

 of being blended with, the higher beds (with some exceptions, which 

 are probably attributable to the displacement and reconstruction of 

 the original deposit), they are found in the lowermost stratum — 

 that which rests immediately upon the Cretaceous or Tertiary beds, 

 and which would be left bare when these became dry land. 



It is true that occasionally, although comparatively rarely, im- 

 plements are found lying above the lowest bed ; but this is not in- 

 consistent with the belief that they were originally deposited at the 

 lower level, which I regard as their ordinary or normal position. 

 Unlike marine deposits, which are usually those of accretion, the 

 changes which are effected by river- or deluge-agency are those of 

 denudation and dislocation ; and it is evident that after the lowest 

 stratum was constituted it was overwhelmed by other very con- 

 siderable masses, which could only have been transported by powerful 

 torrents. These, in their course, conveying rocks of considerable 

 magnitude, could not fail to some extent to break up the subjacent 

 beds, and in this way some implements would be taken from their 

 first place of deposit, and left at relatively higher levels. As every 

 inundation disturbs, and partially, if not entirely, effaces the traces of 

 that which preceded it, so the upper portion of any bed may be 

 carried away and form a new deposit, upon which the lower portion 

 may afterwards be thrown, and thus the position of each becomes 

 reversed. The worn appearance of some specimens, as compared 

 with the fresh and sharp condition of others, tends to show that, 

 while the latter have been but little, if at all, displaced, the former 

 have been subjected to much rolling and attrition. 



The circumstance that some implements are found lying above 

 the lowermost stratum of gravel is thus not inconsistent with the 

 belief that the stones from which they were wrought were neverthe- 

 less taken from that bed, and that they are thus to be ascribed to the 

 commencement of the Quaternary period. On the other hand, if we 

 should reject this view, we should be forced to conclude that the 

 process of manufacture was continued through the very lengthened 

 periods that would be requisite for the excavation of the existing 

 river-vaUeys, involving the assumption, so difficult of acceptance, 

 that although these implements were fabricated and used by many 

 successive generations, they all passed away without leaving any 

 other trace of their existence ; and we must also suppose a constant 

 recurrence of those agencies, whatever they may have been, by 

 means of which these things were buried under thick masses of 

 gravel and sand. 



Under all the circumstances, therefore, it seems probable that the 

 implements for the most part were not transported by any river or 

 flood, but that they were made, or left, at or near the spots where 

 we find them, although in some instances, especially in valleys 

 and watercourses, they may have been afterwards displaced. 



But even if it were otherwise, if it were certain that they were 

 brought into their present position at the same time with the beds of 

 gravel in which they occur, and by the same means, the belief that 



