Southern's Experiments on the Density of Steam. 115 



very nearly 130*7 cubic inches; but as the piston did not rise 

 high enough to touch the top that closed the cylinder, and 

 there was also unavoidably a space between the valve and the 

 cylinder, these spaces together were computed to equal 1"7 

 cubic inch. Of course, had the elasticity of the steam been 

 just equal to that of the atmosphere, no addition to the 130'7 

 cubic inches would need to be made; but as in the three succes- 

 sive experiments it was about i, 4, and f greater, these propor- 

 tions of the spaces would escape when the valve was open that 

 allowed the discharge of the steam to be made into the atmo- 

 sphere, and must therefore be added respectively to the con- 

 tents discharged by the motion of the piston. 



These additional quantities are 1*7 x ^=-'51 ; 1*7 x | = 2"83 ; 

 and 1-7 xf = 5-1; which, added to 130-7, gives 131-27 in the 

 first experiment ; 133-53 in the second, and 135*8 in the third, 

 for the quantity of steam discharged at each stroke of the pis- 

 ton; and therefore the number of strokes which would dis- 

 charge one cubic foot in each of the three experiments, would 

 be 13-164, 12*941, and 12*724. respectively. 



The steam was conducted from the cylinder, after passing 

 the valve, by means of an iron pipe attached to a small copper 

 one, having its end bent down, and immersed a short depth 

 into a cistern of water. The cistern was made of fir- wood, 

 and painted inside and outside with white paint; was about 30 

 inches square, and 26 inches deep ; and the quantity of water 

 in it was ascertained by weighing it, as was also the accession 

 to it by the condensed steam. 



The elasticity of the steam was ascertained by measuring 

 an actual column of mercury which it supported; and the 

 number of strokes was ascertained by a machine called a 

 counter. 



The following table contains the principal facts of these ex- 

 periments : 



