48 Dr J. W. Dawson on the Antiquity of 3fan. 



water flows, even occasionally, through a srite of caverns, no 

 layer of pure stalagmite can be produced ; hence the forma- 

 tion of such a layer is generally an event posterior in date 

 to the cessation of the old system of drainage — an event 

 which might he brought about by an earthquake causing 

 new fissures, or by the river wearing its way down to a 

 lower level, and thenceforth running in a new channel. 



" In all the subterranean cavities, more than forty in 

 number, explored by Schmerling, he only observed one 

 cave, namely, that of Chokier, where there were two regular 

 layers of stalagmite, divided by fossiliferous cave-mud. In 

 this instance, we may suppose that the stream, after flow- 

 ing for a long period at one level, cut its w^ay down to an 

 inferior suite of caverns, and, flowing through them for cen- 

 turies, choked them up with debris ; after which it rose 

 once more to its original higher level : just as in the Moun- 

 tain Limestone district of Yorkshire some rivers, habitually 

 absorbed by a ' swallow hole,' are occasionally unable to dis- 

 charge all their water through it ; in which case they rise 

 and rush through a higher subterranean passage, which was 

 at some former period in the regular line of drainage, as is 

 often attested by the fluviatile gravel still contained in it. 



" There are now in the basin of the Mouse, not far from 

 Liege, several examples of engulphed brooks and rivers : 

 some of them like that of St. Hadelin, east of Chaudefontaine, 

 which reappears after an underground course of a mile or two ; 

 others, like the Yesdre, which is lost near Goftontaine, and 

 after a time re-emerges ; some, again, like tlie torrent near 

 Magnee, which, after entering a cave, never again comes to 

 the day. In the season of floods such streams are turbid at 

 their entrance, but clear as a mountain-spring where they 

 issue again ; so that they must be slowly fllling up cavities in 

 the interior with mud, sand, pebbles, snail-shells, and the 

 bones of animals which may be carried away during floods. 



" The manner in which some of the large thigh and shank 

 bones of the rhinoceros and other pachyderms are rounded, 

 while some of the smaller bones of the same creatures, and 

 of the hysena, bear, and horse, are reduced to pebbles, 

 sliows that tliey were often transported for some distance in 

 the channels of torrents, before they found a resting-place. 



