MECHANICS AND USEFUL ARTS. 53 



sularand Oriental Steam Navigation Company" have used snpei'- 

 licated steam for many years, and its Diri^ctors certify that it lias 

 saved them many thousand tons of coal. In this country, the 

 steamers of the "Bay Line," running; between Baltimore and For- 

 tress Munroe, employed superheated steam with an economy of 

 30 per cent, in their fuel. The steam, which was superheated by 

 means of an arrangement of tubes in the uptake, was maintained 

 at a temperature of 400 degrees in the cylinder ; yet a subsequent 

 inspection of its interior surface, after using this steam for several 

 months, showed it to be as smooth and polished as a mirror. The 

 writer's experience in the jiractical application of superheated 

 steam with stationary boilers has shown that where the steam 

 was superheated by the fuel about 100 degrees above the tem- 

 perature due to its pressure (giving a temperature of 400 

 degrees in the cylinder(, the saving in feed-water, or steam, was 

 nearly one-third, and the economy in fuel was one-quarter, 

 showing that from five to eight i)er cent, of the fuel was required 

 for supi^rheating the steam generated by the remainder, thereby 

 increasing its efficiency nearly one-third. With this temperature 

 maintained in the cylinder, by a judicious ari'angement of the 

 superheating apparatus, the operation of the engine was highly 

 satisfactory, no water being present to necessitate the opening of 

 water-cocks, or bring undue strains upon the cylinder-heads or 

 connections. It is hardly necessary to add that no appreciable 

 action could be observed upon the lubricants, packing, or working 

 surfaces of the engine. 



The full economy due to the use of steam expansively cannot 

 be realized when it is employed in the saturated condition, owing 

 to its partial condensation during expansion. As heat and jjower 

 are correlative terms, steam cannot perform work without the 

 diminution of a portion of its heat, besides that lost by radiation. 

 This heat, coiTcsponding to the work done, may be taken from 

 superhe;ited steam without destroying its efficiency ; for it will 

 still remain in the cylinder, pui-e and dry, to the end of the stroke. 

 It can be confidently asserted, that no steam engine is entitled to 

 that name, if it employs a mixture of water and vapor instead of 

 the genuine article. The objections sometimes advanced on the 

 score of " want of durability" in superheating apparatuses may 

 be entirely removed by the exercise of a proper care in their 

 construction and application, and by the allowance of a liberal 

 amount of heating surface ; so that it is not necessary to subject 

 the superheaters to an undue degree of heat, which would natu- 

 rally tend to their destruction. These particulars faithfully com- 

 plied with, it will be found that no tangible objections can be 

 ojiposed to the employment of moderately superheated steam ; 

 and, when such economical results obtain from its use, it seems 

 imaccountable that it is not more generally appreciated, and that 

 the manufactui'ing public still adhere to the old saturated article, 

 wasting by it botli their time and money. The jiractical advan- 

 tages attending the use of superheated steam, either when used 

 as power, or for heating and drying purposes, are immense ; and 

 it is to be hoped that, with the increased diifusion of knowledge, 

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