240 DESCRIPTION OF A NITRE CAVE. 



they say it is in the "lei/," and when it is left to settle previous 

 to crystallization, a large quantity of salt will be deposited in 

 the settling troughs, which they call " cubic salts,." These 

 salts are again thrown upon the ash-hoppers and are supposed 

 to assist in precipitating the lime from the nitrate of lime, and 

 in the opinion of the workmen, are changed into pure saltpe- 

 tre. They consider this salt as nitre killed, as they express it, 

 by the excessive strength of the ley. To make 100 pounds of 

 good saltpetre at the great cave, eighteen bushels of oak ashes 

 are necessary; ten of elm, or two of ashes made by burning 

 the dry wood in hollow trees. In the discovery of the value 

 of this latter kind of ashes, the philosophers and chemists of 

 Europe have been anticipated by the saltpetre-makers of Ken- 

 tucky.* The earth in some caves does not require half this 

 quantity of ashes to precipitate the impure salts. 



When wood ashes cannot be readily obtained near the 

 caves, the liquor which runs from the earth in the hoppers is 

 boiled clown to the point of crystallization, and suffered to be- 

 come solid by cooling. In this form, which is called " thick 

 stuff," it is transported to a part of the country, where ashes 

 can be procured, dissolved in ley sufficiently strong to precipi- 

 tate the lime, settled in troughs and then boiled down and crystal- 

 lized. This thick stuff is extremely liable to deliquesce in warm 

 moist weather, and is therefore commonly melted down and 

 put into casks before it is carried from the caves. Horned cat- 

 tle are very fond of it, and a small portion of it is almost in- 

 stantly fatal to them. Those who have had frequent opportu- 

 nities of seeing cattle perish in this way, remark that the blood 

 when drawn from their veins, is of a very black colour, and 

 flows with great difficulty. A substance possessing such active 

 properties, might deserve the attention of experimental physi- 

 cians, and may possibly merit a share of that praise which has 

 been so liberally and perhaps so injudiciously bestowed upon 

 the nitrate of pot-ash. 



After these observations on the calcareous nitre beds in Ken- 

 tucky, and the modes commonly employed for obtaining that 

 salt, I shall mention some of the most remarkable circumstan- 



• See Vol, X. p. 330. Philosophical Magazine, 



