COMMON SALT MIXED WITH SNO"\\ r , 131 



careful in that respect than myself. But I never had any ni- 

 tre of that appearance, and least of all any that had in it a 

 mixture of common salt; so that I could not doubt but that 

 this was the same salt that I had used before for the pur- 

 pose above mentioned. That this change must have come 

 from the snoio with which it had been dissolved, could not be 

 doubted; and therefore I resolved to repeat the experiment 

 with the next that should fall, but seeing that Dr. Mitchell 

 had procured an acid from hail stones, 1 was instantly deter- 

 mined to excite other persons to repeat the experiment as well 

 as myself, having now more confidence in my own. 



What was the acid that Dr. Mitchell procured he did not 

 ascertain, mine was unquestionably the nitrous, and it must have 

 displaced that of the common salt by a superior affinity to its 

 base. This acid must be exceedingly volatile; for I could not 

 produce the same effect by repeated solutions and evaporations 

 of the same kind of salt in snow water of long standing, a 

 quantity of which I have always had, to use occasionally in- 

 stead of distilled water. 



The manner in which nitrous acid may be formed in the 

 atmosphere is easily explained on my hypothesis of the com- 

 position of that acid; since I have always procured it by the 

 de-composition of dephlogisticated and inflammable air, to- 

 gether with a small mixture of marine acid (which must there- 

 fore be formed from some of the same elements) as Mr. Cav- 

 endish procured it by the de-composition of dephlogisticated 

 air, both of us using electric sparks. 



Now it is probable that, although most kinds of air, even 

 those that have no chemical affinity, will remain diffused 

 through each other, without any sensible separation, after be- 

 ing mixed together, yet in the upper regions of the atmos- 

 phere, above that of the winds, there may be a redundancy 

 of inflammable air, which -is so much lighter than any other 

 kind of air, as Mr. Kirwan and others suppose, and that there 

 is a proportion of dephlogisticated air, in the same region can- 

 not be doubted. In this region there are many electrical ap- 

 pearances, as the aurora borealis, falling stars, kc. and in the 

 lower parts of it thunder and lightening ; and by these means, 



