288 ST. ACHEUL. 



principally the flint implements are found. This layer also 

 contains many well-rolled tertiary pebbles. 



In the early Christian period this spot was used as a 

 cemetery : the graves generally descend into the marly sand, 

 and their limits are very distinctly marked, as in fig. 140/; 

 an important fact, as showing that the rest of the strata have 

 lain undisturbed for 1500 years. Some of the coffins were 

 of hard chalk (fig. 140 e), some of wood, in which latter case 

 the nails and clamps only remain, every particle of wood 

 having perished, without leaving even a stain behind. 

 Passing down the hill towards the river, all these strata are 

 seen to die out, and we find ourselves on the bare chalk ; 

 but again at a lower level occurs another bed of gravel, 

 resembling the first, and capped also by the bed of brick 

 earth which is generally known as loess. This lower bed of 

 gravel is that called by Mr. Prestwich the lower level gravel. 



These strata, therefore, are witnesses ; but of what ? Are 

 they older than the valley, or the valley than they ? are they 

 the result of causes still in operation, or the offspring of 

 cataclysms now, happily, at an end ? 



If we can show that the present river, somewhat swollen 

 perhaps, owing to the greater extension of forests in ancient 

 times, and by an alteration of climate, has excavated the 

 present valley, and produced the strata above enumerated ; 

 then " the suggestion of an antiquity for the human family 

 so remote as is here implied, in the length of ages required 

 by the gentle rivers and small streams of eastern France to 

 erode its whole plain to the depths at which they now flow, 

 acquires, it must be confessed, a fascinating grandeur, when, 

 by similitude of feature and geology, we extend the hypo- 

 thesis to the whole north-west frontiers of the continent, and 

 assume, that from the estuary of the Seine to the eastern 

 shores of the Baltic, every internal feature of valley, dale 

 and ravine in short, the entire intaglio of the surface has 



