260 



Fourthly.— It is the opinion of Dr. Dupont, if we rightly comprehended 

 him, that the '' Loesg" which underlies the stalagmite of the caverns, and 

 consists of stiff clay and stratified sands, the same which contained the human 

 jaw and the bones of the Rhinoceros tichorinus, is of marine origin. I do 

 not know what reasons Dr. Dupont has for holding this opinion, but we shall 

 soon be made acquainted with them, as that gentleman is about to publish a 

 work upon the physical geology, as well as the animal conteats of these 

 Belgian caves. 



This is an important point, for if the basement gravsl and silts in the 

 caverns turn out to be marine, I see no way of escaping fiom the conclusion 

 that the valley of the Lesse was submerged beneath the waters that deposited 

 the pebble and drift beds on the summit of the limestone platform that rises 

 above the caverns, and consequently that these cavern drifts are pre-glacial. 

 We arrived at other conclusions upon which, however, I am unwilling to lay 

 much stress, as our survey was necessarily short. 



It appears from the statements I gathered from Dr. Dupont that on the 

 flanks of the Lesse valley, above the bone caverns, but below the platform 

 drifts, there are high level vallet/ gravels, which tell of an ancient river which 

 flowed at a higher level than the waters of the existing river, and which old 

 river is not unlikely to have washed down pebbles and drifts derived through 

 streams and lateral sources from the platform drifts on the high country 

 around. Again, the pebble beds which lie at the base of the deposits of the 

 "Trou desNutons" and the "Trou de Naulette," do not appear to me to 

 have a marine aspect, they have the arrangement of an old river shingle. My 

 impression is that this shingle was derived from the platform drifts on the 

 upper surface of the country, and was washed into the caverns by the agency 

 of the underground streams which opened out into the valley of the ancient 

 Lesse. This is supported by the evidence of the animal remains found in the 

 basement deposits. Remains of the beaver were found by Dr. Dupont, and 

 this testifies more of fresh water conditions than marine. Again, we believe 

 that the "Xoms" or stratified clay and sUt which contained the human jaw 

 and mammalian bones, is a fluviatile silt, the deposit of waters which once 

 swept into or through the caves before those relative changes of land and 

 water level were brought about, which caused the floodings by turbid waters 

 to cease, and the flaor of the caves to become dry land, and the stalagmite to 

 gather above the human and animal relics with its encrusting seal 



Altogether we believe the history of the cavern deposits on the Lesse to 

 belong to that ancient river history which geologists now comprehend as the 

 period of the low level drifts of Prestwich, a period when, as we know in this 

 country, climatal adaptations and the animals of the period were very different 

 from the present. Since that period the great mammalia, which once inha- 

 bited Europe, have become extinct, and aU our rivers, like the river Lesse, 

 flow in deeper hollows excavated in the hard strata which forms the bottom 



