808 Transactions of the American Institute. 



effect upon some parts of the system ; but it is confined to the con- 

 densing engine, and ought not to get out. 



The President — Mr. Hughes, formerly of [Rochester, undertook to 

 use the heat from waste steam to e vaporize the bi-sulphide of carbon, 

 and after a great many trials, made sixteen years ago, came to the 

 conclusion that the same amount of heat applied to water would do 

 just about as much. 



■Mr. T. D. Stetson — Mercury boils at about 600° Fahr. ; sulphuric 

 acid at about 300° ; water at 212° ; alcohol at 180° ; bi-sulphide of 

 carbon at 110° ; sulphuric ether at about 90° ; the hydrocarbons at 

 different temperatures down to 32° F. ; and carbonic acid at 148° 

 below zero. It is impossible in practice to communicate all the heat 

 from one fluid to another, but by passing it through very small tubes 

 and thin vessels we may transfer a large part of it. Now, suppose we 

 make our fire under a boiler to volatilize mercury at 600° and 

 upwards, and exhaust right down to atmospheric pressure. Then we 

 may take the exhaust from the mercury, and obtain a vapor frpm sul- 

 phuric acid, which will give us additional power. Exhaust from that 

 to atmospheric pressure, and it will make steam at 300°, a pressure of 

 four or five atmospheres. The exhaust steam at 212° gives us a 

 pressure of several atmospheres in heating bi-sulphide of carbon ; and 

 so we may go on, step by step, down the scale until we reach a point 

 where we shall find a difficulty in condensing; for something will 

 depend upon our supply of cold. Working in the winter, on the 

 banks of the river, with an unlimited supply of ice-cold water, we 

 may go down nearly to 32°, perhaps ; but ordinarily we may have to 

 stop at 70 or 80°. 



I have carried this out to extremes, to illustrate the principle. The 

 reason why we do not adopt this method of working is that it don't 

 pay. It costs too much for the apparatus, for the wear and tear, and 

 for the attendance. The nearest approach to this bi-sulphide of car- 

 bon engine is the Dr. Trombly engine, in which sulphuric ether was 

 used, heated by the exhaust steam. This was introduced in a large 

 steamer running upon the Mediterranean, the water of which was 

 cold enough to condense the ether. It required a good deal of con- 

 densing surface, and that is one of the difficulties of this method of 

 working ; but he did the. work, saved his ether, and used it over and 

 over again, with a considerable increase of power. I presume the 

 difficulty in that case was the same as in all analogous cases, in 

 making it pay. 



We must consider the first cost of the apparatus, the interest upon 



