164 On the Construction of Gasonietefs. 



u^iial manner, (for B is no more than the common gas- 

 holder.) screw in the collar </, shut the cock c, and open gy 

 the water will run in until the density of the gas in B is ca- 

 pable of resisting its eftective pressure, which will always be 

 exactly equal to a column of water whose height is equal to 

 the height of the orifice c, of the tube de, above that of the 

 recurved tube in the vessel B: for as the air in entering the 

 vessel A has to counteract a column of water equal to the 

 depth e below the surface, so will the ga& in B be pressed 

 with the whole column, minus that part of it above e } for the 

 superincumbent column above e has no share in the pressure, 

 which mav be increased and decreased at pleasure by ele- 

 vating and depressing e, without regard to the quantity of 

 water in A, and which pressure will continue uniform until 

 the water subsides to the level of the orifice e.— -See the de- 

 scription of my hydrostatic regulator, Phil. Mag. voL xx:. 



p. esg. 



From the facility with which the pressure in this gaso- 

 meter may be altered, it becomes a very useful instrument 

 in all cases where the blowpipe is used; whether when 

 charged with oxygen gas for the purpose of deflagrating or 

 of deoxidating metais, the combustion of the diamond, or 

 other experiments where intense heat is required ; or whe- 

 tiicr it is charged v/ith atmospheric air for miniature, glass- 

 blowing, soldering, or the like. It will also be found useful 

 for filling vessels for a variety of experiments in pneumatic 

 chemistry, as well as for playiiig jets of flame, Sec. If a 

 cock, provided with a jet capable of being inclined in any 

 angle to the horizon, be fixed into the x.\xh^ fg near g, and 

 the tube de so elevated that the orifice e arrives near or 

 within the bottom of the vessel A, a useful and accurate 

 apparatus will be formed for Illustrating the parabolic tlteory 

 of projectiles ; for, a.i the pressure and efflux is uniform, the 

 horizontal ranges will be equal at equal angles above and 

 below 45", and the curve described distinct and well de- 

 fined. An instrument of this kind has been employed in' 

 the Mathematical Society's present course of lectures, and 

 is now in their repository. 



XXVII. Pro- 



