%^6 Memoir on the Quantity of 



decreafe in proportion as the rcfpevSlive quantities of the ful- 

 phurct fliall be greater, 



I fhall now proceed to explain my method of operation, 

 which, after fcveral trials, appeared to me the limpleft and 

 tlie moft correct. I have employed it for a long time without 

 having oblerved the difference of a hundredth in the rcfults. 



My whole apparatus is a glafs tube five lines in diameter, 

 and ten inches in length : it is clofcd atone of its extremities, 

 and divided on the lide into lOO equal parts, each of a line, 

 and which all together are capable of containing about an 

 ounce of water. As the common air is found every where, 

 to take a quantity correfponding to the lOO divifions nothing 

 is neceflarv but to fill the tube with water, keeping it in a 

 perpendicular pofition, with the aperture downwards. The 

 finger applied to the aperture muft be removed at intervals, 

 and the tube inclined a little, by which means the external 

 air, if the tube be at the furface of the water, will enter it ; and, 

 when it occupies the lOO lines, it muft be flopped, keeping the 

 orifice clofed by the finger. The tube muft be immerfed in the 

 water tub, that it may allume the fame temperature. When 

 it is taken out, it muft be examined whether the air furpafTes 

 or not the fpace of too lines, to take away or add the 

 quantity neceflary to make it fiand exactly on a level with the 

 place where the divifions begin. I then introduce this air 

 in the ufual manner into a flafk containing from twice to 

 four times its volume of liquid fulphuret of lime, previoufiy 

 impreunated with azotic gas. I then ftop it, and lliake it for 

 live minutes ; after which I transfer the air back into the 

 graduated tube, and find that the aeriform fluid, which 

 before occupied loo divifions cxa<Slly, occupies, after the opera- 

 tion, only 79; and, confequently, 21 parts havedifaj^peared. 

 If the graduated tube ends in a neck with a ground ftopper, 

 inftead of water it may be firft filled with fulphuret, and 

 by proceeding as above the operation will be fpeedier, without 

 bavinp- occafion to employ water, or to introduce air into the 

 Hafks, and to transfer it. To try another refpirable air, 

 however, not atmofpheric, fimilar transfers are indifpen fable, 

 as i» evident, and they may be executed with the greatcft con- 

 venicneCj by means of Funtana's fmall meafurc. 



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