by E. Cornelius. 321 



subterranean voyage for twelve hours. He stated that the 

 course of the cave after proceeding some way to the southwest, 

 became south ; and southeast by south, the remaining distance. 



Natural Nitre. 



The sides of the principal excavation present a few apart- 

 ments which are interesting, principally because they furnish 

 large quantities of the earth from which the nitrate of potash 

 is obtained. This is a circumstance very common to the caves 

 of the western country. In that at Nicojack, it abounds, and 

 is found covering the surfaces of fallen rocks, but in more 

 abundance beneath them. There are two kinds, one is called 

 the " clay dirt," the other the "black dirt ;" the last is much 

 more strongly impregnated than the first. For several years 

 there has been a considerable manufacture of saltpetre from 

 this earth. The process is by lixiviation and crystallization, 

 and is very simple. The earth is thrown into a hopper, and 

 the fluid obtained, passed through another of ashes, the alkali 

 of which decomposes the earthy nitrate, and uniting with its 

 acid, which contains chiefly nitrate of lime, turns it into nitrate 

 of potash. The precipitated lime gives the mass a whitish co- 

 lour, and the consistence of curdled milk. By allowing it to 

 stand in a large trough, the precipitate, which is principally 

 lime, subsides, and the superincumbent fluid, now an alkaline, 

 instead of an earthy nitrate, is carefully removed and boiled for 

 some time in iron kettles, till it is ready to crystallize. It is 

 then removed again to a large trough, in which it shoots into 

 crystals. It is now called " rough shot-petre." In this state 

 it is sent to market, and sells usually for sixteen dollars per 

 hundred weight. Sometimes it is dissolved in water, reboiled, 

 and recrystallized, when it is called refined, and sells for twenty 

 dollars per hundred. One bushel of the clay dirt yields from 

 3 to 5lbs. and the black dirt from 7 to lOlbs. of the rough shot- 

 petre. The same dirt, if returned to the cave, and scattered 

 on the rocks, or mingled with the new earth, becomes impreg- 

 nated with the nitrate again, and in a few months may be throwo 

 into the hopper, and be subjected to a new process. 



