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"iiii alteration, increase, or diminution; It is sr species 

 by itself ; iui is of a nature totally distinct from that of 

 yii other bodies. 



That this is absolutely necessary both to feed common* 

 fire, and to sustain the life of animals-, may be learned 

 from an easy experiment. Place a cat, together with a 

 lighted candle, m a cold oven ; then lute the door close,, 

 having fixed a glass in the middle of it; and if you look 

 through this, you may observe at one and the same in- 

 stant, the candle goes out, and the animal dies. A plain 

 proof, that the same tire is needful to- sustain both culi- 

 nary fire and animal life: and a large quantity of it, 

 Some doubtless pervades the oven door, but not enough 

 >o sustain either iiame or life. Indeed, every animal is a 

 kind of lire engine. As soon as the lungs inspire the air, 

 tlu? fire mingled with it is imtuntly dispersed through f he 

 pulmonary vvssds mlo the blbo\i ' thence it is diiiu* i 

 through every part of the body, even the most -minute 

 arteries, veins and nerves. In the mean time the lungs 

 inspire more air and fire, and so provide a constant supply. 



The air seems to be universally impregnated with this- 

 fire, but so diluted, as not to hurt the animal in respira- 

 ration. So a small quantity of a liquor dropt in water 

 may foe friendly to a human body, though a few drops 

 of the same liquor given by themselves, would have, oc- 

 casioned certain death. And yet you cannot conceive 

 one pai tide -of the water\ without a particle of the 'me- 

 dicine. It is not impossible, this may be one great use 

 of air, by -adhering so closely to the elementary fire, to 

 temper and render salutary to the body, what would 

 'otherwise be fatal to it. 



To put It beyond dispute, that this fire is largely 

 ''mixed with the air, you may make the following experi- 

 ment. Take around lump of iron, and heat it to a de- 

 gree called a we Ming heat* take it out of the fire, and 

 with, a pair of beiious, blow cold air upon it. .The iron 

 ^'ili then melt, as if rt were in the hottest 



fire. Now when taken out of the forge, it had not fire 

 "enough" m it to ro-v.u.u;r the ccaesimvof its parts ; but 

 1 3 



