500 TRANSACTIONS OF THE AMERICAN INSTITUTE, 



heat, but that would be too dear. The working matters are a 

 combination of air and steam ; if the heat is let in below, car- 

 bonic acid will first be formed ; if the coal is vigorous in combus- 

 tion, the engine is stopped by simply turning a cock. I think 

 that an engine constructed on the Barker mill principle, will 

 work and make the cheapest engine possible. I may say that 

 gas has been used in engines which use this combustion princi- 

 ple. The gas fixture was lighted by an electrical spark j but one 

 difiiculty was that sometimes the spark Avould not ignite the gas 

 under the cylinder. Take a spirit lamp in there and it will burn 

 if you allow the valves to be open above and below. If you shut 

 them, it will burn for a minute with a great deal of smoke and 

 then go out. By a mechanical invention, the same movement 

 that stops the engine opens the valves, and the air is allowed to 

 come in contact with the fire. Coal oils are not as cheap as coal. 

 I am satisfied that coal oil used at $8 a gallon, will come cheaper 

 than coal at $5 per ton. Coal oil is a hydro-carbon. One pound 

 of hydrogen will go six times as far as one pound of carbon. In 

 the ordinary caloric engine, I do not think that a temperature of 

 over three hundred deg. is obtained. I think coal oils are of 

 great value, and that they will shortly be used on steamers, the 

 only difiiculty being in the practical methods of using them. In 

 the caloric engine, they must have a large friction surface. I 

 wish to say in reference to the Barker mill principle, that the 

 furnace is independent in size and shape of the power which you 

 get. By this system you may make your furnace to hold ten tons 

 if you please. 



Mr. Babcock. — The principle of using the products of combus- 

 tion is 100 years old. The great difficulty is to keep the proper 

 temperature so as not to over-heat the different parts of the 

 engine. The heater is worn out in about six months, but the 

 great economy consists in the decrease of manual labor. Sir 

 George Kaley had tried several experiments in England previous 

 to 1846, but did not succeed because the excessive heat destroyed 

 his packing. A few years ago Mr. Bennett built an engine at a 

 cost of $50,000, it was put on a railway, and after running a few 

 miles it went off" the track into the ditch and was sold for old 

 iron. A gentleman has one running in Boston which makes 300 

 revolutions a minute. We are not to look for any great advan- 

 ta,ge by using air on Captain Ericsson's principle. The rate of 

 destruction is various : some run out in a few weeks, and others 



