ON FURNACES. 401 



ever, very remarkable. In 1869 an extended trial was made, at Chat- 

 ham Dockyard, of the system of Messrs. Dorsett and Blyth, for heating 

 with creosote or other heavy oils. The furnaces to which the plan 

 was applied were those used for heating ship plates and armour plates 

 for bending. The oil was vaporized in a small boiler or generator, 

 and supplied to the furnaces through jets one-eighth of an inch in 

 diameter, at a pressure of thirty pounds per square inch ; and the 

 air, not previously heated, was simply drawn in by the chimney 

 draught. The heating, both of the armour plates and of thin ship 

 plates, was done in one-third the time taken in heating in the 

 ordinary way, with coal ; and the weight of oil burned, per ton of plates 

 heated, was between one-sixth and one-eighth of the former con- 

 sumption of coal. More recently, in the course of last year, a report 

 by Professor H. Wurtz has been published,* of the working, in America, 

 of Eames's system of firing furnaces with petroleum, which quite 

 corresponds with the results obtained at Chatham. On Eames's plan, 

 the crude petroleum used is evaporated and carried into the furnace 

 by a current of highly superheated steam, at a pressure of ten pounds 

 per square inch. The furnace to which it was applied was one for 

 heating scrap iron piles, for rolling into plates ; and the air supply, as 

 at Chatham, was cold. The furnace was heated up, ready for charging, 

 in forty-five minutes, and with a consumption of only twenty-two and 

 a half gallons of oil. The output, per shift of ten hours, was eight tons 

 of rolled plates, with a consumption of 300 gallons=2ooo pounds of oil : 

 the same furnace, when fired with coal, having heated the piles for only 

 six tons of plates per shift, and burned five and a half tons of coal. 

 The effective heating value of equal weights of oil and coal was thus 

 in the proportion of eight to one. 



The much less weight of mineral oil than of coal that is required, ac- 

 cording to these two statements, to do an equal amount of work, is pro- 

 bably due in part to the combustion of the oil-vapour being effected with 

 the admission of a smaller excess of air than is found in the products of 

 combustion from a furnace fired with coal ; to the combustion taking 

 place wholly in or at the entrance to the working chamber ; and to the 

 work being done in less time, so that there is less loss of heat by outside 



* Engineering and Mining Journal (New York), Aug. Jth, 1875, p. 122. 



cc 



