Polytechnic Association. 811 



The President — There was a hot-air engine brought here from Bos- 

 ton some years ago which gained fifty per cent by using the discharged 

 hot air in making steam ; and it was suggested that by applying all 

 the heat to water instead of the air they might gain the other fifty per 

 cent. (Laughter.) 



Mr. J. K. Fisher — The great difficulty about Dr. Trombly's engine 

 was that they could not prevent leakage, and it interfered with the 

 health of the men. 



The President — Ericsson's hot-air ship would not go without a great 

 deal of oil ! 



Mr. J. K. Fisher — I do not believe you can do any more with ether 

 or bi-sulphide of carbon than with the hot water that comes from the 

 condenser. I do not think there is any gain in using the bi-sulphide 

 of carbon. 



A member suggested that the application of the principle that arti- 

 ficial draft produces great economy of fuel, to hot air engines, would 

 extend their usefulness. 



Mr. J. B. Root — That principle was admitted here in the former 

 discussion, but I think it is a mistake. 



Separating Cockles from Wheat. 



Mr. Henry, of Tennessee, described a new apparatus by means of 

 which cockles are separated from wheat. There are two cylindrical 

 rollers, about eight inches in diameter, one of which is of iron and 

 the other of vulcanized rubber. The cockle, being a rough grain, 

 imbeds itself in the rubber, and is carried over and swept off. The 

 cockle is of as large diameter as the wheat, and it has hitherto been 

 difficult to separate it. It poisons hogs and poultry, and no use has 

 been found for it after it is separated from the wheat. 



Danes' Puddling Furnace. 

 Mr. Samuel Danks explained his new puddling furnace, which sub- 

 stitutes steam for man power. He had conceived the idea in 1856, 

 and in 1857 was nearly ready to start when the financial crash stopped 

 his operations. He has recently carried the plan into successful 

 operation. The iron is placed in a hollow cylinder, hung and revolv- 

 ing upon an axis at right angles to its central line, so that the melted 

 metal is thrown from end to end at each half revolution. By this 

 process, five tons can be as readily puddled at once by steam power 

 as 500 pounds could formerly by hand.' The result is shown at Chat- 

 tanooga to be the removal of impurities more perfectly than ordinary 



