OXYGEN AND THE NATURE OF ACIDS. 121 



phenomenon, I considered it as something very extraordinary; but as a 

 property that was peculiar to air that was extracted from these sub- 

 stances and adventitious; and I always spoke of the air to my acquaint- 

 ance as being substantially the same thing with common air. I par- 

 ticularly remember my telling Dr. Price that I was myself perfectly 

 satisfied of its being common air, as it appeared to be so by the test of 

 nitrous air; though, for the satisfaction of others, I wanted a mouse to 

 make the proof quite complete. 



On the 8th of this month I procured a mouse and put it into a 

 glass vessel containing two ounce-measures of the air from mereurhts 

 calcinatus. Had it been common air a full-grown mouse, as this was, 

 would have lived in it about a quarter of an hour. In this air, however, 

 my mouse lived a full half hour, and though it was taken out seemingly 

 dead, it appeared to have been only exceedingly chilled; for, upon 

 being held to the fire, it presently revived and appeared not to have 

 received any harm from the experiment. 



By this I was confirmed in my conclusion that the air extracted 

 from mercurius calcinatus, etc., was al least as good as common air; 

 but I did not certainly conclude that it was any better; because, though 

 one mouse would live only a quarter of an hour in a given quantity of 

 air, I knew it was not impossible but that another mouse might have 

 lived in it half an hour, so little accuracy is there in this method of as- 

 certaining the goodness of air: and. indeed, I have never had recourse 

 to it for my own satisfaction since the discovery of that most ready, 

 accurate and elegant test that nitrous air furnishes. But in this case I 

 had a view to publishing the most generally-satisfactory account of my 

 experiments that the nature of the thing would admit of. 



This experiment witli the mouse, when I had reflected upon it 

 some time, gave me so much suspicion that the air into which I had 

 put it was better than common air, that I was induced, the day after, 

 to apply the test of nitrous air to a small part of that very quantity of 

 air which the mouse had breathed so long; so that, had it been common 

 air, I was satisfied it must have been very nearly, if not altogether, as 

 noxious as possible, so as not to be affected by nitrous air; when, to my 

 surprize again, I found that though it had been breathed so long it was 

 still better than common air. For after mixing it with nitrous air, in 

 the usual proportion of two to one, it was diminished in the proportion 

 of 4^ to 3^; that is, the nitrous air had made it two ninths less than 

 before, and this in a very short space of time: whereas I had never 

 found that in the longest time any common air was reduced more 

 than one fifth of its bulk by any proportion of nitrous air, nor more 

 than one fourth by any phlogistic process whatever. Thinking of 

 this extraordinary fact upon my pillow, the next morning I put 

 another measure of nitrous air to the same mixture, and, to my utter 



