122 THE ANTIQUITY OF MAN. 



200 feet or more in height above the present streams. There 

 appears also, in many cases, to be such a correspondence in the 

 openings of caverns on opposite sides of some of the valleys, 

 both large and small, as to incline one to suspect that they 

 originally belonged to a series of tunnels and galleries, which 

 were continuous before the present system of drainage came into 

 play, or before the existing valleys were scooped out. Other 

 signs of subsequent fluctuations are afforded by gravel containing 

 elephants' bones at slight elevations above the Meuse and several 

 of its tributaries. The loess also, in the suburbs and neighbour- 

 hood of Liege, occurring at various heights in patches lying at 

 between 20 and 200 feet above the river, cannot be explained 

 without supposing the filling up and re-excavation of the valleys 

 at a period posterior to the washing in of the animal remains 

 into most of the old caverns. It may be objected that according 

 to the present rate of change, no lapse of ages would suffice to 

 bring about such revolutions in physical geography as we are 

 here contemplating. This may be true. It is more than pro- 

 bable that the rate of change was once far more active than it 

 is now. Some of the nearest volcanoes, namely, those of the 

 Lower Eifel about sixty miles to the eastward, seem to have been 

 in eruption in post-pliocene times, and may perhaps have been 

 connected and coeval with repeated risings or sinkings of the 

 land in the basin of the Meuse. It might be said, with equal 

 truth, that according to the present course of events, no series 

 of ages would suffice to reproduce such an assemblage of cones 

 and craters as those of the Eifel (near Andernach for example) ; 

 and yet some of them may be of sufficiently modern date to 

 belong to the era when man was contemporary with the mammoth 

 and rhinoceros in the basin of the Meuse. 



" But although we may be unable to estimate the minimum of 

 time required for the changes in physical geography above 

 alluded to, we cannot fail to perceive that the duration of the 

 period must have been very protracted, and that other ages of 

 comparative inaction may have followed, separating the post- 

 pliocene from the historical periods, and constituting an interval 

 no less indefinite in its duration." 



"As the osseous and other contents of Kent's Hole had, by 

 repeated diggings, been thrown into much confusion, it was 

 thought desirable in 1858, when the entrance of a new and intact 



