On Sal Nitrum and Nitro- Aerial Spirit 117 



glass, as was shown above ; then let another small 

 portion of the air produced as before be conveyed in 

 like manner to the glass, and let this process be repeated 

 until the air is present in sufficient quantity. 



And that we may now make our experiment, let a 

 small animal, say a mouse placed in a small cage, be 

 placed in the upper part of the cavity of an inverted glass 

 with a suitable support below it, as is delineated in Plate 

 v.. Fig. 6. And let the glass with the animal inside be 

 so immersed in the water, that the water inside may 

 rise as high as the support on which the mouse rests, 

 which can be done by means of the curved syphon de- 

 scribed in Chapter VII. ; and let everything remain in 

 this condition till the animal dies, and let the length 

 of time during which the animal breathes in the glass 

 be carefully noted. Now let the dead animal be re- 

 moved and another living animal be put in its place. 

 And let it as before be shut in the glass immersed in 

 the water, care being taken that the same quantity of 

 air as before may be enclosed in the glass. This done, 

 let the aforesaid air be transferred, as described, into 

 the glass containing the animal, in such quantity that 

 the air thus introduced shall by two or even three times 

 exceed the quantity of ordinary air enclosed from the 

 first in the glass. And then let the glass be raised till 

 the water (which is depressed by the air introduced) 

 reaches the support on which the animal rests, care 

 being taken that the mouth of the glass be not lifted 

 above the water. And let everything continue thus 

 till the animal dies. When this has occurred we shall 

 find that the animal has not lived much longer in the 

 glass on the second occasion than the other did on the 

 first ; that is to say, before the aforesaid air was intro- 

 duced into the glass. But if that air were truly 

 air suitable for sustaining life, the animal put in on 



