0& STEAM-ENGINES. 317 



fleam of a high temperature into fuch receptacle or fteam cafe, Mr. Woolfs 

 which is always attended with a rifle of explofion proportioned ■" ^^"en-* 

 to the elasticity of the (team employed, I put into the faid gines. 

 furrounding receptacle, or cafe, oil or the fat of animals, or 

 wax or other fubftances capable of being melted by a lower 

 temperature than the heat intended to be employed, and of 

 bearing that heat without being converted into vapour : or I 

 put into the faid cafe or cafes mercury or mixtures of metals, 

 as of tin, bifmuth, and lead, capable of being kept in a ftate 

 of fufion in a lower temperature than that intended to be era- , 

 ployed in working the fleam-engine ; and I fo form the fur- 

 rounding cafe or cafes as to make it or them admit the aforefaid 

 oil, or other fubftance employed, to come into contact not 

 only with the fides of the fteam veflel or vefTels; or work- 

 ing cylinder or cylinders^ out alio with the bottom and top 

 of the fame, fo that the whole may be as much as poflible 

 maintained in one uniform temperature; and this tempera- 

 ture I keep up by a fire immediately under or round the 

 cafe or cafes that contains the aforefaid oil or other fub- 

 ftance, or by connecting the faid cafe or cafes with a fe« 

 parate vefTel or vefTels, kept at a proper temperature, filled • 

 with the oil or other fubftatice made ufe of as aforefaid. 

 In fome circumftances, or whenever the fame may be con- 

 venient or defirable, I employ the fluid metals; or mixtures 

 of metals, and oil or other of the fubftances before enu- 

 merated, at one and the fame time in the fame engine; that 

 is to fay, in the part of the cafe or veflel expofed to the 

 greateft action of the fire, I fometimes have the aforefaid 

 metals or mixtures of metals, and in the parts lefs expofed' 

 to the action of the fire, I put oil, or other fubftances ca- 

 pable of bearing the requifite heat without being converted 

 into vapour. 



* By this arrangement, and method of applying the fur- 

 rounding heat, I not only obviate the necefiity of employ- 

 ing fteam of a 'great expanfive force round the fleam veflel 

 or vefTels, or the working cylinder or cylinders, as already 

 mentioned, to maintain them at the temperature required, 

 but I am enabled to obtain from fleam of a comparatively 

 k>w temperature, or even from water itfelf, admitted into 

 the fteam veflel or vefTels, all the elfecls that can be ob- • . ' 



tained from .fteam of a high temperature, without any of 



the 



