DESCRIPTION OF A NITRE CAVE. 245 



rives great probability from an experiment of Bishop Watson, 

 by which it would appear, that soda was actually converted 

 into pot-ash. It is likewise corroborated by the apparent con- 

 version of lime and soda into pot-ash in our calcareous caverns, 

 and by the change of what the workmen call cubic salts, into 

 nitrate of pot-ash. Thouverel affirms that he witnessed the 

 real conversion of washed chalk into pot-ash, in his experi- 

 ments on nitrous vapours, and Chaptal observed the same phe- 

 nomenon when exposing chalk to the vapours of putrid bul- 

 lock's blood. Now as the nitric acid combines readily with 

 lime, soda and magnesia, as well as with pot-ash, it may be 

 easily conceived, that it still retains its affinity for those substan- 

 ces, in every form which they may assume, whilst changing 

 into each other, and that the "tertium quid" formed by the 

 union of nitric acid and lime in the intermediate stage beliveen 

 lime and put-ask, may possess properties very different from ni- 

 trate of lime or nitrate of pot-ash. The same may be remark- 

 ed with regard to soda and magnesia. Here every chemist 

 will recollect the ingenious observations of Dr. Mitchel, con- 

 cerning nitric acid and the essential differences between that 

 substance and septic acid at the moment of its formation. No 

 person can doubt of the possibility of charging nitrogene with 

 different portions of oxegen. The explosive efficient pro- 

 perty of nitre may depend on a certain dose of this principle. 

 But even admitting that pot-ash and nitric acid never vary in 

 their nature, it may still be contended, that powder-makers 

 have no means of ascertaining what proportion of acid and 

 alkali that nitre ought to contain, which would form the best 

 gun-powder. And whilst this is confessed, it surely can avail 

 us little, to be very scrupulous in the adjustment of the propor- 

 tions of the nitre to the charcoal and sulphur. The consumers 

 of pot-ash, in every part of the world have remarked varieties 

 in the quality of the salt, for which no particular cause can 

 be assigned. It is very much to be regretted, that a regular 

 series of experiments has never been instituted, to discover what 

 kind of ashes would yield an alkali most proper for the for- 

 mation of nitre. Charcoal should be examined with a similar 

 view. Mr. Coleman has published experiments and remarks 



