CONCLUSION. 543 



volumes of water down their valleys, but great as the floods 

 were they did not as a rule succeed in filling the valleys to 

 overflowing. 



Thus the evidence supplied by the river- and flood-deposits 

 is in perfect keeping with the testimony of the organic remains. 

 We find the valley-slopes coated in some places with consider- 

 able accumulations of calcareous tufa, charged with leaves of such 

 plants as the laurel, the fig, the sycamore, the ash, the willow, 

 etc., and many land-shells, and indicating doubtless a prolonged 

 period of repose, when the rivers flowed with an equable volume, 

 and were not subject to excessive floods. And we read the 

 same tale of quiet and orderly conditions in the finely -bedded 

 deposits of gravel and sand which form no inconsiderable por- 

 tion of the Pleistocene river-accumulations. On the other hand, 

 the tumultuous coarse gravels, with their disturbed bedding and 

 ice-floated erratics, betoken turbulent waters and river-ice, and 

 the gradual melting of interbedded masses of frozen snow, while 

 the thick and widely-spread loams tell us of enormous floods 

 and inundations. And these latter excessive conditions super- 

 vened certainly more than once. The hill-loss shows that they 

 occurred in early Pleistocene times, and the position of the 

 valley-loss proves that the closing scene of the Pleistocene 

 Period was one of torrential rivers and vast inundations. 



The cave-accumulations indicate in like manner the recur- 

 rence during the Pleistocene Period of cold climatic conditions 

 and flooded rivers, which alternated with prolonged epochs of 

 repose. And they likewise show that the Pleistocene Period 

 came to a close with severe conditions of climate. This is indi- 

 cated not only by the character of the organic remains, which 

 are met with in the uppermost layer or layers, but by the occur- 

 rence in certain caves of glacial and fluvio-glacial deposits, 

 underneath which the Pleistocene ossiferous deposits are buried, 

 as in the Victoria Cave in Yorkshire, and many of the Belgian 

 caves. I believe also that the coarse breccia and the numerous 

 large limestone-blocks which overlie the Pleistocene fossiliferous 

 strata in many caves, owe their origin in chief measure to the 



