63 



The effect of infiltration through the roof would now cement into 

 a breccia the mingled remnants from the upper chamber, and enclose 

 them, as it were, in a marble monument, in their new, though not 

 their latest resting-place. 



But the infiltration proceeding from the roof would act first, and 

 most powerfully, in cementing the upper part of the intruded mass. 



The lower portion would be less consolidated, and therefore less 

 capable of resisting any pressure from above. 



6th Period. In the progress of time, some torrent of extra- 

 ordinary magnitude may have penetrated through the upper cavern, 

 and, filling the channel or pipe P, have acted by its hydrostatic 

 pressure on the semi-consolidated matter in the lower one. As the 

 water accumulated in the pipe, the pressure would become immense, 

 and ultimately the materials included in the lower cavern would give 

 way at their point of least resistance. This would probably be 

 towards the middle or bottom of the original entrance. The first 

 sudden rush would probably clear out the greater part of the con- 

 tents of the lower cavern, leaving, however, 



1st. Those portions attached to the roof by the infiltrated 

 matter. 



2nd. Those portions on the floor more consolidated by pressure 

 than the middle which gave way ; and also other portions of the 

 loose rubbish which the form of the floor at the entrance of the 

 cave might have intercepted in its course. 



After this reopening of the lower cavern, the access of air would 

 accelerate evaporation from its roof, and that portion of the breccia 

 still adhering to it would gradually acquire the external coating of 

 stalactite which usually occurs in caves. 



In the meantime the dropping from the roof, falling upon the 

 floor, might also contribute to consolidate the remaining fragments, 

 and, although more slowly, cover the whole of them with a stalag- 

 mitic floor. 



In this state, on entering the lower cave, the walls would be found 

 perforated by marine animals, and no traces of animal life or of human 

 art would present itself ; but on excavating the floor, both would be 

 found below the stalagmite ; whilst if the curious inquirer should 

 drive his pick into the roof, its fragments would bear testimony to 

 the same fact. 



