[ i6 4 ] 



quantity of lime-water, will affect it in fuch a man- 

 ner, that breathing into it will not make it turbid, 

 which otherwife it always prefently does. 



Dr. Hales fuppofed, that by burning brimftone 

 repeatedly in the fame quantity of air, the diminu- 

 tion would continue without end. But this I have 

 frequently tried, and not found to be the cafe. In- 

 deed, when the ignition has been imperfect in the 

 firfl inftance, a fecond firing of the fame fubflance 

 will increafe the effect of the firft, &c. but this pro- 

 grefs foon ceafes. In many cafes of the diminution 

 of air, the effect is not immediately apparent, even 

 when it ftands in water -, for fometimes the bulk of 

 air will not be much reduced, till it has palled fe- 

 veral times through a quantity of water, which has 

 thereby a better opportunity of abforbing that fluid 

 part of the air, which had not been perfectly de- 

 tached from the red. I have fometimes found a 

 very great reduction of a mafs of air, in confequence 

 of palling but once thorough cold water. If the air 

 has flood in quickfilver, the diminution is generally 

 inconfiderable, till it has undergone this operation, 

 there not being any fubftance expofed to the air that 

 could abforb any part of it. 



I could not find any confiderable alteration in the 

 fpecific gravity of the air, in which candles, or brim- 

 ilone, had burned out. I am fatisfied, however* 

 that it is not heavier than common air, which mufl 

 have been manifeft, if fo great a diminution of the 

 quantity had been owing, as Dr. Hales and others 

 fuppofed, to the elafticity of the whole mafs being 

 impaired. After making feveral trials for this pur- 

 pofe, I concluded that air, thus diminifhed in bulk, 



is. 



