THE RETROSPECT OF THE YEAR. 85 



roof. This has stood because its limestone is more crys- 

 talline than that above and below it. It is flinty and is 

 probably corniferous. 



Stalactites and stalagmites are formed in the old cham- 

 bers of the caves by the percolation of water through the 

 fissures in the rocks, while the degradation and channeling 

 are going on in the new chambers. In the case of the 

 Natural Bridge, this action went on faster than the build- 

 ing process, hence the roof became too thin to sustain its 

 weight and fell in, leaving the fragment forming the bridge 

 to tell the story. The professor then told the company of 

 the formation of caves in general, many of which he has 

 explored, making particular mention of the Mammoth 

 cave and of peculiar formations found in it. 



Rev. B. F. McDauiel explained the formation of tufa 

 and the varieties of incrusting minerals in caves. Col. 

 H. C. Parsons, the proprietor, told of the caves in the 

 neighborhood. Several of them have been opened, 

 but not thoroughly explored. Until they can be prop- 

 erly opened up, he deems them unsafe for amateur ex- 

 plorers. 



This estate of Mr. Parsons, of some 2,000 acres, corn- 

 pi ises a horse-shoe range of lofty, wooded hills, enclosing 

 the basin on whose slopes lie the hotels and the owner's 

 residence. The Horse Shoe opens towards the east and 

 commands a errand and beautiful view of the Blue Ridgfe, 



o O ' 



forest-covered and mist-crowned, rising 4,300 feet above 

 the sea. A little to the left the glint of broken granite 

 alone shows where the river burst through, and at the 

 right the crest lowers so that the Peaks of Otter may 

 overlook. 



