134 Mr. Arthur Woolf's Impr overrents hi the 



volume ; and that, generally, as to all the intermediate or 

 higher degrees of elastic force, the number of times which 

 steam of any temperature and force can expand itself is 

 nearly the same as the number of pounds it is able to sus- 

 tain on a square inch exposed to the common atmospheric 

 pressure : provided always that the space, place, or vessel in 

 which it is allowed to expand itself, be of the same tempera- 

 ture as that of the steam before it be allowed room to expand. 

 Respecting the different degrees of temperature required 

 to bring steam to, and maintain it at, different expansive 

 forces above the weight of the atmosphere, Mr. Woolf has 

 found, by actual experiment, setting out from the boiling- 

 point of water, or 21 2°, at which degree steam of water is 

 only equal to the pressure of the atmosphere, that in order 

 to give it an increased elastic force equal to five pounds the 

 square inch the temperature must be raised to about 2274°, 

 when it will have acquired a power to expand itself to five 

 times its volume, still be equal to the atmosphere, and ca- 

 pable of being applied as such in the working of steam- 

 engines, according to his invention : and with regard to 

 various other pressures, temperatures, and expansive forces 

 of steam, the same are shown in the following table : 



Tabic of the relative pressures per square inch, temperatures 

 cud expansibility of steam at degrees of heat above the 

 lolling point of water, beginning with the temperature of 

 steam of an elastic force equal to five pounds per square 

 inch, and extending to steam able to sustain forty pounds 

 on the square inch. 



Steam of 

 an elastic 

 force pre- 

 dominat- 

 ing over 

 the pres- 

 sure of 

 lie atmo- 

 sphere 

 upon a 

 safety- 

 valve, 



Pounds per 



square Inch. 



5 



6 



7 



8 



9 



10 

 15 

 20 



25 



30 



. 35 . 



UoJ 



requires 

 to be 

 maintain 

 ed by a 

 tempera- 

 ture equi 

 to about 



< 



Degrees 

 of Heat. 



230-1 

 23 2 £ 

 235-j; 



2374 

 23 pi 

 250-1 

 25Qi- 

 267 

 2/3 

 2/8 

 L2S2 ' 



Expan- 

 sibility. 



times its 

 volume, 

 and con- 

 tinue 



and at 



these re 



spective 



degrees of fa 



r'f ( ' 1 15 f elastic* 

 steam can 



expand 



itself to 



about 



20 

 25 

 30 

 35 



Uo. 



ty 



to the 

 pressure 

 of the at- 

 )here 



mosi. 



And so in like manner, by small additions of temperature, 



an expansive power may be given to steam to enable it to 



expand to 50, 60, 70, 80, 90, 100, 200, 300, or more times 



3 its 



