Analyfis of the Air. 157 

 rations, into the nature of a fluid, too fine 

 to be the object of our fight, muft be by 

 finding out fome means to eftimate what 

 influence the ufual methods of analyfing 

 the animal, vegetable and mineral kingdoms, 

 has on that fubtile fluid; and this I effe&ed 

 by affixing to retorts and boltheads hydro- 

 ftatical gages in the following manner, viz. 

 In order to make an eftimate of the quan- 

 tity of Air, which arofe from any body by 

 diftillation or fufion, I firft put the matter 

 which I intended to diftill into the fmall re- 

 tort r (Fig. 33.) and then at *z cemented 

 faft to it the glafs veffel a b, which was very 

 capacious at b, with a hole in the bottom. 

 I bound bladder over the cement which was 

 made of tobacco-pipe clay and bean flower, 

 well mixed with fome hair, tying over all 

 four fmall flicks, which fervcd as fplinters 

 to ftrengthen the joynt 5 fometimes, inftead 

 of the glafs veffel a b, I made ufe of a large 

 bolthead, which had a round hole cut, with 

 a red hot iron ring at the bottom of it 5 

 through which hole was put one leg of an 

 inverted fyphon, which reached up as far 

 as z. Matters being thus prepared, holding 

 the retort uppermoft, I immerfed the bolt- 

 head 



