MECHANICS AND USEFUL ARTS. 65 



and tliat further wheels of this kind will be sent over for trial 

 under English rolling stock. We have samples of the iron from 

 Avliich these wheels are cast, and it is of magnificent quality. 

 The fracture is a rich dai'k gray, medium-grained, and shows 

 great toughness, the particles aj^pearing to have been irregularly 

 torn, rather than broken short off. The specific gravity ranges 

 from 7.25 to 7.3185, and the tensile streno'th from 32,000 to 35,- 

 102 lbs., or, say, fourteen and one-half to sixteen tons per square 

 inch. The iron is that known as the Salisbury cold-blast charcoal 

 iron, and is worth about £10 per ton in New York. — Engineer- 

 ing, 1866. 



STEEL LOCOMOTIVE WHEELS. 



Railway companies in England have for some time largely 

 employed steel as a substitute for ordinary iron, for the working 

 parts of locomotives, with most satistactory results. On heavy 

 freight-lines it has been found that with the ordinary iron tires, or 

 the engine-wheels, the distance run was not more thaii 90,000 

 miles, — in many cases noj, more than 60,000 miles, — and the 

 wheels require to be taken from under the engine for every 20,- 

 000 or 30,000 miles run, for repairs and "turning up." In the 

 case of steel tires, however, the Avheels will run 100,000 miles, 

 before they require " turning up " or repairing. The "Hallway 

 News " states that the result of a very careful examination of the 

 efiects of wear, lead to the opinion that these wheels will run 

 from 350,000 to 500,000 miles, or equal to some twelve or fifteen 

 years' work of a daily average of about one hundred miles. The 

 difi'erence of cost between the two metals is not great ; in the one 

 case it ranges from £40 to £-15 per ton, while the steel is about 

 £55 ; the cost of labor in placing the tires being about the same in 

 each case. It is confidently stated that a similar saving in point 

 of wear may be made by substituting steel for iron in boilers, 

 axles, cranks,, eccentrics, and other j)ortions of locomotives. — 

 Mechanics'' Magazine, April, 1865. 



HIGH TEMPERATURES TRODUCED BY GAS. 



There is no reason why the very highest temperatures should 

 not be produced by the combustion of gas ; and in reality it has 

 been found that by regulating the supply of air and gas, and pre- 

 venting the caloric evolved from being dissipated, a very great 

 heat may be obtained. For this purpose, it is only necessary to 

 combine a number of flames produced by Bunsen bui'ners, but 

 without permitting them to comj)letely penetrate one another, 

 and causing a draught by means of a sheet-iron tube about two 

 metres high. The heat, by a projoer management of the flame, 

 and by the products of combustion being made to act on Ijoth 

 sides of the refractory envelope within which the substance to be 

 operated on is placed, becomes extremely powerful. With such 

 an arrangement it was found that two square metres of gas, burned 

 under a pressure of five or six centimetres of water, fused six 

 hundred and seventy grammes of silver in fifteen minutes ; and 

 6* 



