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Lll. Descr'ifjtion of an Itntn/ment for equalizing the Pres- 

 sure ami Efflux of non-elastic Fluids. By Mr. Joseph 

 Steevens. 



To Mr. Tilloch. 



EUKWiTH you have a drawing and description of an 

 instrument for equalizing the pressure and cfBux of non- 

 clastic fluids. Tlie principles on which it depends are the 

 sanife as that which I constructed for the Mathematical 

 Society about four years since, but which had no provision 

 tor refillincr during an experiment, Should it merit a place 

 in your valuable publication, it is very nuich at your ser- 

 vice. At some future time I purpose to submit to your con- 

 sideration a gasometer much simplilicd by various altera- 

 tions, and rendered more vmiversal by the addition of this 

 instrument. I am, sir. 



Your obedient servant, 

 26, Garlick Hill, JosEl'H StEEVENS. 



Dec. 7, 1804. 



Having frequently had occasion to regulate the pressure 

 and efflux of water with some degree of accuracy, and find- 

 ing it usually attended with much difficulty, I was induced 

 to try what could be done by the re-action of the atmo- 

 sphere. The instrument represented in the annexed draw- 

 hig (see Plate VIII.) is the result of several trials, and ap- 

 pears to be at once simple and accurate, and is at the same 

 time, I conceive, applicable to every purpose for which 

 such an instrument can be required. 



There are several other construction's far more elegant 

 and equally useful with that of which I have made choice. 

 I have preferred distinctness of parts to symmetry, my 

 principal object being the explanation of the principle rather 

 than the construction of the machine. AB is a glass or 

 metal cylinder about i21 inches lono; and 4 inches diameter, 

 cemented at the bottom into a brass socket on the foot C, 

 and at the top into the cap A, through a collar of leathers 

 in which is inserted a copper tube, (■}', about 3-lOths of an 

 inch in diameter in the bore.' ff is a cock screwed into the 

 socket Ij, the. orifice of which is about ^l- 1th of that of the 

 tube ef. . . .,' ^.^ . 



j^ Ilavlng tbq. machine thus constructe'tl^ uiliscrew the nut d, 

 jnd' fill llic vessel nearly full of water V screw it again into 

 its place, and thrust the tube f'/down until its lower end is 

 a little below the cock g; winch may now be opened, and 

 • ^VoK-'2u. No. bO. J«//. 1805. T a small 



