n6 POPULAR SCIENCE MONTHLY. 



tation in water, the process of vegetation, and probably other natural 

 processes, by taking out the superfluous phlogiston, restore it to its 

 original purity. But I own I had no idea of the possibility of going 

 any farther in this way, and thereby procuring air purer than the best 

 common air. I might, indeed, have naturally imagined that such would 

 be the air that should contain less phlogiston than the air of the atmos- 

 phere; but I had no idea that such a composition was possible. 



It will be seen in my last publication that, from the experiments 

 which I made on the marine acid air, I was led to conclude that com- 

 mon air consisted of some acid (and I naturally inclined to the acid that 

 I was then operating upon) and phlogiston; because the union of this 

 acid vapor and phlogiston made inflammable air, and inflammable air, 

 by agitation in water, ceases to be inflammable and becomes respirable. 

 And though I could never make it quite so good as common air, I 

 thought it very probable that vegetation, in more favorable circum- 

 stances than any in which I could apply it, or some other natural process, 

 might render it more pure. 



Upon this, which no person can say was an improbable supposition, 

 was founded my conjecture of volcanoes having given birth to the at- 

 mosphere of this planet, supplying it with a permanent air, first in- 

 flammable, then deprived of its inflammability by agitation in water, 

 and farther purified by vegetation. 



Several of the known phenomena of the nitrons acid might have 

 led me to think that this was more proper for the constitution of the 

 atmosphere than the marine acid; but my thoughts had got into a differ- 

 ent train, and nothing but a series of observations, which I shall now 

 distinctly relate, compelled me to adopt another hypothesis, and brought 

 me, in a way of which I had then no idea, to the solution of the great 

 problem, which my reader will perceive I had had in view ever since my 

 discovery that the atmospherical air is alterable, and, therefore, that it 

 is not an elementary substance, but a composition, viz., what this compo- 

 sition is, or what is the thing that tec breathe, and how it is to be made 

 from its constituent principles. 



At the time of my former publication I was not possessed of a 

 burning lens of any considerable force; and for want of one I could not 

 possibly make many of the experiments that I had projected, and which, 

 in theory, appeared very promising. I had, indeed, a mirror of force 

 sufficient for my purpose. But the nature of this instrument is such 

 thai it cannot be applied, with effect, except upon substances that are 

 capable of being suspended or resting on a very slender support. It 

 cannot be directed at all upon any substance in the form of powder, nor 

 hardly upon anything that requires to be put into a vessel of quicksilver; 

 which a ]) pears to me to be the most accurate method of extracting air 

 from a great variety of substances, as was explained in the introduction 



