Polytechnic Association. 807 



them into vapor. Water requires a temperature of 212° to 

 vaporize at atmospheric pressure, and 966 units of heat become 

 latent. But ether will vaporize at 96°, and only 165 units of 

 heat are required. That is an amazing saving of fuel. On that 

 idea, some fifteen years ago, an ether engine was built at the Novelty 

 Works in New York. But practical difficulties came up. First, it 

 was difficult to get the joints tight ; and when it leaked it took fire, 

 and alarmed every one. Another difficulty was that the latent heat 

 was so much by weight, and the vapor of ether is nearly seven times 

 as heavy as steam. It is a curious property of vapors, that whatever 

 the temperature of vaporization, and whatever amount of heat becomes 

 latent, in units, the amount of latent heat in a cubic foot of vapor is 

 always the same ;- and as engines are driven, not by the weight of the 

 vapor but by its volume, that takes away all the supposed advantage 

 of volatile fluids with regard to their latent heat. 



The first objection was that we might as well use the steam from a 

 high pressure engine to drive a low pressure engine. The simple 

 answer to that is, that all the pressure you get from the waste steam 

 becomes back pressure on the first engine, and you have all the 

 machinery and friction for nothing. But if you pass your waste 

 steam freely through tubes which heat bi-sulphides of carbon, there 

 is no back pressure, and the pressure you obtain from the vaporization 

 of the bi-sulphide of carbon is a clear gain. Fairbank & Dunkin in 

 England founded a method of judging of the performance of steam 

 engines, by measuring the water of condensation, as it was done in 

 the recent trial at the American Institute Fair. In the best steam 

 engine, the water condensation is warmed somewhat, and that amount 

 of heat is lost. Now let us see what is the pressure with different 

 vapors : 



Ether. Bi-Sulphide of Carbon. Water. Pressure. 



95 degrees 110 degrees 212 degrees 1 atmosphere. 



115 degrees 130 degrees 210 degrees 2 " 



125 degrees 140 degrees 265 degrees 3 " 



133 degrees 148 degrees 280 degrees 4 " 



Now, if we take the steam at' 212, you see that it will produce a 

 pressure of much more than four atmospheres in the bi-sulphide of 

 carbon. It is asserted that, by this engine, a nearer aj:>proach has 

 been made to theoretic perfection, in the power produced, than ever 

 before. 



Mr. J. K. Fisher — What is the odor of bi-sulphide of carbon? 



Dr. Van der Weyde — It is very offensive, and has a paralyzing 



