THE CAVKS AND POTHOLKS AT ROCKWOOD. 251 



caveis are the walls, which form escarpments along the ravine, 

 through which a rivulet passes at the present time. Near by a great 

 cavern (Poole's) explains the process ; the entrance is narrow and low, 

 yet 12 feet in, and you reach a much wider passage, and as you pro- 

 ceed immense apartments are entered, so that you pass along a 

 tortuous pathway for several hundred yards. Some of the apartments 

 are 20 by 30 feet high and 40 wide. No running stream is seen to 

 indicate the cause, but the water trickling down the sides explains 

 this great disintegration of the limestone ; so here, coming nearer 

 home, at Rockwood, you find caves not so extensive, but as character- 

 istic of the action of waters as those I have been referring to. 



The ))resence of mud in the back part of the inner caverns at Rock- 

 wood seems to indicate a connection between them and the surface 

 through tissui-es in the rock. This mud bears a close resemblance to 

 the .soil which covers the rock above, and has likely been brought 

 down by rain through these cievices. This rain charged with carbonic 

 acid in time could easily dissolve out the rock and leave the caverns 

 as we find them now. Frost would assist in breaking off fragments 

 as we find them now scattered along the floor of the cave, while the 

 sides present a veiy irregular apj)earance. 



The presence of stalactites on the roof and stalagmites on the floor, 

 also shows much dissolving of rock by water, for these structures are 

 merely the precipitated lime from the water, which has carried it 

 down. The water on reaching the roof evaporates, and the lime is 

 left, this goes on adding jjarticles of lime, until a structure is formed 

 not unlike an icicle in form, but composed of carVjonate of lime. 

 Sometimes the drops fall upon the floor and form something of the 

 same in form. The stalactites ai-e sometimes hollow but the stalag- 

 mites are solid ; this is owing to the one being formed on the roof 

 and the other on the floor. In some cases, those from the roof fall 

 and become imbedded in the material on the floor. At Rockwood 

 the stalagmites are more common than the stalactites, seeming to 

 indicate that the water containing lime in solution falls before 

 evaporation takes place, and consequently a tendency for an accumu- 

 lation of lime on the floor. 



Potholes. 



The Potholes, too, are no doubt the result of the action of the 

 water, but in this case the action is more mechanical than chemical. 



