190 ON STTPRUHEATEI) STEAM. 



To enable you to see the more readily the nature 

 and formation of superheated or sub- saturated 

 steam, as distinguished from the ordinary or satu- 

 rated steam, we will at once refer to the expe- 

 riment of the two chambers before us, which are 

 now in operation. 



You will not, I am sure, find fault with me 

 for giving you the experiment in so working 

 and practical a form : for persons who are to 

 be amused only, something in glass or silver 

 would have done better. 



In the vessel to the left you have the ordi- 

 nary or saturated steam as a boiler; in the 

 vessel to the right you have sub-saturated steam, 

 or steam only. 



The vessels, are connected with a pipe, and 

 both are consequently of the same pressure, 

 but both are not consequently of the same heat ; 

 for you will perceive that the thermometer in 

 the vessel with water is not so high (although 

 of the same pressure) as the thermometer in the 

 vessel with steam only. 



If the steam-pipe which connects the two 

 vessels be closed and the communication shut 

 off, with the heat continued equally under both 

 vessels, the saturated steam of the boiler will 

 increase rapidly to a great pressure, and in an 

 increasing ratio the higher it goes ; but the sub- 

 saturated of the other vessel will only increase in 



