PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 477 



bino, forming' water and at the same time gene;fating- the most intense lieat 

 known, and by which platinum and rock crystal (quartz) are not only 

 melted but sublimed; and for the invention of the intenselj^ brilliant calcium 

 light, now commonly but improperly known as the Drummond light, which 

 consists in burning the same gases in the presence of the oxide of calcium 

 or lime. This prize fund of the Boston academy has now increased to 

 830,000, and recentl}' the members of the academy have been demanding 

 more energy on the part of the Rumford committee. Capt. Ericson, of 

 New York, applied for the prize for the invention of an air-engine, and the 

 prize was awarded to him, not because he had constructed the best air- 

 engine, but because his inventions and exertions had given such an impe- 

 tus to efforts in this department, that they might be considered as having 

 led the way to all subsequent improvements. 



Air Engines. 



A committee of the Academj^, by careful trials, found that Ericson's air 

 engine yielded one horse power by the consumption of fourteen pounds per 

 hour. Roper's engine, in which the products of combustion are used, 

 yielded one horse power by the combustion of five pounds of coal per hour, 

 and that air and steam engine of Shaw required but two and a half pounds 

 of coal per hour to produce one horse power. He believed the latter is the 

 best engine in which air is used that has yet been made, but he did not 

 claim to be a mechanician, and would be glad to hear the views of other 

 gentlemen present regarding this engine. 



Prof. Charles A. Seeley said the great diflSculty which Mr. Ericson had to 

 encounter was the heating of a large quantity of air very rapidly. A small 

 quantity could be heated readily, but then at the risk of burning out or 

 consuming the iron which surrounded the air to be heated. The trne 

 principle of heating air is to make it go through the fire. Capt. Bennett 

 and others had long ago tried the plan of using the gases generated in the 

 furnace, but they had met with difiiculties which have been surmounted by 

 ilr. Shaw. 



Mr. Murdock stated that the Boston Academy Committee experimented 

 with Mr. Shaw's engine, using first only air and afterwards mixing steam 

 with the air, and found by the latter method the economy for this engine, 

 which has already been stated. 



The Chairman suggested that if by using the heat of the gaseous pro- 

 ducts of combustion which have done their work on the air piston, bypass- 

 ing such products under a steam boiler, more than double the power was 

 produced by the engine than when air alone was used, it might be more 

 economical to dispense with the air engine apparatus, and use all the heat 

 in generating steam. It appeared to him that the addition of steam power 

 to caloric engines was a step in the right direction. 



Pumps. 



The regular subject of the evening was opened by Dr. Jos. W. Richards, 

 who occupied nearly all the remaining time of the evening in describing 

 the various kinds of sucking and forcing pumps now in use. They are all 

 too well known to require full descriptions here. One of the most simple 



