VOL. XLI.] PHILOSOPHICAL TRANSACTIONS. 341 



wind-guns, strongly charged, for half a year together, in which the air had lost 

 none of its elasticity : others have found the air as strong after a year ; and a 

 person of credit has asserted, that a wind-gun having been laid by and forgotten 

 for 7 years, when it was found, discharged its air as many times, and with as 

 much force, as it used to do. Now, though air, compressed by any external 

 force, does always increase in elasticity, as it diminishes in bulk ; yet it may, 

 by fermentation, diminish its bulk very much, without gaining any more elasti- 

 city: for if another fluid, whose parts repel one another, but attract the parts of 

 air, be mixed with it, the repulsion of any two particles of air will be diminished, 

 in proportion as a particle of the other fluid, insinuating itself between them, at- 

 tracts them towards itself on either side. The same <;hing will happen to the 

 other fluid, in respect of the particles of air, which mixing with its particles, 

 do in the same manner destroy their repulsion. Thus, if we allow an attraction 

 strong enough between the parts of two elastic fluids, it is possible, that by 

 fermentation a solid may be made out of two elastic fluids, which would have 

 still continued fluid without such a mixture. We are taught by chemistry, to 

 mix fluids together, which immediately coalesce into a solid. When brimstone 

 matches are burning, the effluvia of the sulphur repel each other to great dis- 

 tances, as may be known by the sulphureous smell. Now, though these par- 

 ticles repel each other, they attract the air very strongly, as appears by the fol- 

 lowing experiment. 



Take a tall glass receiver, closed at top, holding about 4 quarts of air ; and 

 having put its open end over a bundle of brimstone matches on fire, standing 

 up in the middle of a large dish with water in it, to keep the air from coming in 

 at the bottom of the said receiver, you will observe, that not only as soon as the 

 matches are burnt out, but a good while before, the air, instead of being ex- 

 panded by the flame of the brimstone, will retire into less compass, the water 

 beginning to rise from the dish up into the receiver, and continuing so to do 

 till some time after the matches are burnt out ; so that there will be in the 

 receiver only 3 quarts of air, instead of 4, more or less, in proportion to the 

 quantity of brimstone burnt. And this plainly happens by some of the effluvia, 

 or little parts of the sulphur, attracting some of the particles of the air, so as to 

 make an unelastic compound, that precipitates into the water. If the elasticity 

 of the air is quite lost when the repulsion of its particles is taken oft', or suffi- 

 ciently counteracted, it must follow, that its elasticity depends on repulsion ; 

 and that this is often the case, appears by a great immber of Dr. Hales's ex-, 

 periments. 



The doctor took a cubic inch of mutton-bone, and having put it into his 

 gun-barrel retort, he distilled out of it 200 or 300 cubic inches of air, inta 

 a large glass bottle, the weight of which air, together with the ashes of the 



