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the glafs. At length, I faw no more bubbles of air than what arofe 

 from the bottom of the water. But what appeared to me in thefe 

 obfervations to be moll worthy of note is, that the bubbles arifmg 

 from the bottom, were at firll fo fmalj, as to be fcarcely vifible to 

 the naked eye,- and by reafon of their fmallnefs, they afcended very 

 llowly ; but as they rofe higher, they gradually became larger, and 

 afcended to the furface M'ith greater velocity. 



I then again thrull; in the pillon with as much force as I thought 

 the glafs would bear, and in doing this, I faw that the whole fpace 

 of air from D E C, and three inches farther from C to B^ \\ as fo 

 comprefled, that the fubtile particles of air which probably had 

 found their way into the glafs, while I withdrew the pilton, had 

 not only again efcaped out of the glafs ; but that alfo the fubtile par- 

 ticles of air mixed with the before mentioned common air from E 

 to D, and alfo the thin particles of air from the bubbles which arofe 

 out of the water, had, by this violent prellurc, been fo forced and 

 driven out of the glafs, tliat there was no more fpace of air than 

 about the fize of two grains of land to be feen in D. 



After this, I again very llowly drew out the pillon, and then 

 again fo many fubtile particles of air got into the glafs, that they 

 filled the whole of the fmaller tube and a fpace in the larger tube, 

 the extent of three inches from C towards B. Again 1 drew the 

 pillon very llowly out of the glafs, left by the too fudden irruption 

 of air, the glafs Ihould be broken. For it had happened to me three 

 feveral times, that by draw ing put the pillon too hallily, the glafs 

 tubes broke at C or D. 



The pains I took to make thefe experiments, was for no other end 

 than to difcover, if poffible, what was the quantity of air extradled 

 from the water : this quantity, though to the eye it feemed confider- 

 able, yet in faft could be but little ; for each of the air bubbles 

 arifmg out of the water is much increafed by being mixed with the 

 particles of common air. Having taken the pillon out of the glafs, I 

 faw the water in the tube fettle itfelf at F ; fo that fuppofmg all the 



