20 



in two different places, at basins of water of unknown 

 extent, and which I should juflge to be nearly on a 

 level with the water of the river ; however, I do not 

 think they are formed by refluent water from that, be- 

 cause they are never turbid ; because they do not rise and 

 fall in correspondence with that in times of flood, or of 

 drought; and because the water is always cool. It is 

 probably one of the many reservoirs with which the 

 interior parts of the earth are supposed to abound, and 

 which yields supplies to the fountains of water, distin- 

 guished from others only by its being accessible. The 

 vault of this cave is of solid lime-stone, from 20 to 40 

 or 50 feet high, through which water is continually per- 

 colating. This, trickling down the sides of the cave, 

 has incrusted them over in the form of elegant drapery ; 

 and dripping from the top of tlie vault generates on 

 that, and on the base below, stalactites of a conical 

 form, some of which have met, and formed massive 

 columns. 



Another of these caves is near the North mountain, 

 in the county of Frederick, on the lands of Mr Zane. 

 The entrance iuto this is on the top of an extensive 

 ridge. You descend 30 or 40 feet, as into a well, from 

 whence the cave then extends, nearly liorizontally, 400 

 feet into the earth, preserving a breadth of from 20 to 

 50 feet, and a height of from 5 to 12 feet. After enter- 

 ing this cave a few feet, the mercury, which in the 

 open air was at 50°. rose to 57*^. of Fahrenheit's ther- 

 mometer, answering to ] 1°. of Reaumur's, and it con- 

 tinued at that to the remotest parts of the cave. The 

 uniform temperature of the cellars of the observatory 

 of Paris, which are ninety feet deep, and of all subter- 

 ranean cavities of any depth, where no chymical agents 

 may be sup})osed to |jroduce a factitious heat, has been 

 found to be 10^. of Reaumur, equal to 54 1-2°. of 

 Fahrenheit. The temperature of the cave above men- 

 tioned so nearly corresponds with this, that the difter- 

 ence may be ascribed to a difl!crence of instruments. 



At the Panther gap, in the ridge which tlividos the 

 waters of the Cow and the Calf pasture, is what is cal- 



