117 



animal, when exposed to the air, is in a certain time 

 carried wholly oft*. And we know that all vegetables by 

 putrefaction become volatile, and so evaporate into air. 



Air, 2. Volatilizes fixed bodies. Thus sea salt being 

 calcined and fused, then exposed to the air to liquify; 

 when liquified, set to dry again ; then fused again, and 

 the operation thus repeated ; will by degrees be almost 

 wholly evaporated, nothing remaining but a little earth. 

 Air, 3. Fixes volatile bodies. Thus though aqua fortis, 

 or spirit of nitre, readily evaporates by the fire ; yet if 

 the air near be impregnated with spirit of urine, the vo- 

 latile spirit is fixed, and falls down in a liquid form. 



But the air's being open or enclosed is of consequence 

 in chymical operations. So, to make sulphur inflamma- 

 ble, a free air is required : in a close vessel it will not 

 kindle. And thus all animals and vegetables can only 

 be calcined in open air. In close vessels they never 

 become any other than black coals. 



By the air-pump the air is in a great measure drawn 

 out of a vessel called the receiver. And hence we learn 

 how much all vital, nutritive, and alterative powers, de- 

 pend upon the air. A candle in the exhausted receiver 

 usually goes out in a minute. A kindled charcoal is to- 

 tally extinguished in about five minutes. Red hot iron 

 is not affected thereby : only it will not light sulphur or 

 gunpowder, but melt it. Loadstones act, as well as in 

 the open air. Smoke sinks in a darkish body to the 

 bottom, leaving the upper part clear and transparent. 

 The syphon does not run therein : but attrition produces 

 beat, as in the open air. "If some grains of a heap of 

 gunpowder be kindled by a burning-glass, they will not 

 tire the contiguous grains. G low-worms lose their light as 

 the air is exhausted ; but recover it not on its re-admission. 

 Vipers and frogs seem dead in less than two hours, but 

 recover in the open air. Snails live ten hours : efts two 

 or three days ; leeches five or six. 



The atmosphere is a body of air and vapours, which 

 surrounds the globe to the height of at least sixty miles, 

 gravitates towards its centre, and is carried along with 



in all its motions. This continually presses on our 



VOL, in. H 



