CAVES. 



471 



enlarge to a great width and height, and wind and 

 branch curiously through the rocks, Generallj^ they 

 are dry, though a few of them are penetrated by rains 

 or crossed by brooks. 



These; cavities in the calcareous mountains are 

 famous for affording an earthy substance, which is 

 useful in the manufacture of salt petre. This earth 

 lies in the bottom of the caves, and its thickness is 

 from two to twenty feet. It is said to resemble 

 black mould or soil. Crystals of salt petre can be 

 frequently seen in it as soon as it is carried out to 

 the light. But if this material be united with a suf- 

 ficient quantity of pot ash prepared on the spot from 

 burned wood, there is produced a copious supply of 

 salt petre. It is computed that there are several of 

 these dark recesses among the limestone mountains, 

 which will afford ten thousand pounds each of this 

 neutral salt, crystallized and fit for market. 



When the earth has thus been letched with the 

 vegetable alkali, and deprived of its acid, it is com- 

 mon with the workmen to replace it. For experi- 

 ence has taught them, that, if put back again into its 

 former situation, it renews its salt petrous quality in 

 about three years. Being impregnated, after lying 

 that duration of time, with another supply of acid, it 

 is fit to be treated once more with wood ashes, for 

 the purpose of forming a second portion of salt petre. 

 There seems to be no end to the possible repetition of 

 these processes, of extracting and re-generating the 

 acid ingredient of the salt.* 



Marked by a bold and singular appearance, the 

 precipice of the Table mountain, called the Lover's 

 * Dr. Mictliell. 



