244 DESCRIPTION OF A NITRE CAVfi. 



tinues to afford it in undiminished quantities. But how shall 

 we reconcile this fact with that before related concerning the 

 production of nitre in the cavities of calcareous mountains 

 which are, in many instances, so closely filled up with clay, 

 that the air can have no access, from which every ray of solar 

 light is excluded, and where the temperature can never exceed 

 57° of Fahrenheit? Is it absolutely certain, that nitre formed 

 by natural processes so very dissimilar, possesses no properties 

 necessarily resulting from the circumstances attendant on its 

 formation? That all the nitrates of pot-ash with which we arc 

 acquainted, have certain properties in which they agree, is un- 

 questionable, but the same may be said of lime and barytes, of 

 soda and pot-ash, and many other substances, which in the 

 early ages of chemical science, were probably identified. 

 Hoffman, long ago proved, that nitrate of pot-ash afforded an 

 alkali very different from that of wood ashes or salt of tartar. 

 The observations of so distinguished a philosopher deserve 

 much attention, and his experiments if repeated by modern 

 chemists could scarcely tail of affording important results: that 

 the sand rock saltpetre differs from that procured from the cal- 

 careous caverns, in the form of the crystal, in hardness and 

 dryness, is known to all who deal in that article, and every 

 powder-maker affirms that it makes better gun-powder. Whe- 

 ther this superiority is owing merely to its greater purity or 

 exemption from an admixture of nitrate of lime, or whether 

 the constituent acid and alkali are modified in some unknown 

 manner, is yet altogether problematical. Chaptal, Thouverel, 

 Guyton, and indeed most of the modern chemists, suppose, 

 that pot-ash is a compound of lime and hydrogen, and that 

 lime itself is formed of carbon, azote and hydrogen, and con- 

 sequently that pot-ash consists of hydrogen, carbon and azote. 

 Mr. Guyton thinks that soda is composed of magnesia and hy- 

 drogen, and that magnesia is a compound of lime and azote, 

 and therefore, that soda is made up of hydrogen, carbon and 

 azote. He is then of opinion that pot-ash, soda, lime and 

 magnesia are nothing more than varied forms and proportions 

 of the same constituent ingredients, differing from each other 

 in the quantities and forces of attraction. This opinion de- 



