122 POPULAR SCIENCE MONTHLY. 



astonishment, found that it was farther diminished to almost one 

 half of its original quantity. I then put a third measure to it; hut 

 this did not diminish it any farther; but, however, left it one measure 

 less than it was even after the mouse had been taken out of it. 



Being now fully satisfied that this air, even after the mouse had 

 breathed it half an hour, was much better than common air, and having 

 a quantity of it still left sufficient for the experiment, viz., an ounce 

 measure and a half, I put the mouse into it; when I observed that it 

 seemed to feel no shock upon being put into it, evident signs of which 

 would have been visible if the air had not been very wholesome; but 

 that it remained perfectly at its ease another full half hour, when I 

 took it out quite lively and vigorous. Measuring the air the next day I 

 found it to be reduced from 1^ to 2-3 of an ounce measure. And 

 after this, if I remember well (for in my register of the day I only 

 find it noted that it was considerably diminished by nitrous air) it 

 was nearly as good as common air. It was evident, indeed, from 

 the mouse having been taken out quite vigorous, that the air could 

 not have been rendered very noxious. 



For my farther satisfaction I procured another mouse, and putting 

 it into less than two ounce-measures of air extracted from mercurius cal- 

 cinatus and air from red precipitate (which, having found them to be of 

 the same quality, I had mixed together) it lived three quarters of an 

 hour. But not having had the precaution to set the vessel in a warm 

 place, I suspect that the mouse died of cold. However, as it had lived 

 three times as long as it could probably have lived in the same quantity 

 of common air and I did not expect much accuracy from this kind of 

 test, I did not think it necessary to make any more experiments with 

 mice. 



Being now fully satisfied of the superior goodness of this kind of air, 

 1 proceeded to measure that degree of purity with as much accuracy as 

 I could, by the test of nitrous air; and I began with putting one meas- 

 ure of nitrous air to two measures of this air, as if I had been examining 

 common air, and now I observed that the diminution was evidently 

 greater than common air would have suffered by the same treatment. 

 A second measure of nitrous air reduced it to two thirds of its original 

 quantity, and a third measure to one half. Suspecting that the dim- 

 inution could not proceed much farther, I then added only half a 

 measure of nitrous air, by which it was diminished still more; but not 

 much, and another half measure made it more than half of its original 

 quantity; so that, in this case, two measures of this air took more than 

 two measures of nitrous air and yet remained less than half of what it 

 was. Five measures brought it pretty exactly to its original dimensions. 



At the same time air from the red precipitate was diminished in the 

 same proportion as that from mercurius catcinatus, five measures of 



