MECHANICS AND USEFUL ARTS. 25 



of engine, of valve-gear, of rate of expansion, of surface conden- 

 ser, of screw propeller, and of boilers, have been thoroughly tested; 

 but the results thus far show that the machinery designed by the 

 Steam Engineering .Bureau of the Department has not been sur- 

 passed, perhaps not equaled, by any of its competitors, while in 

 many cases their results have been greatly below it. 



In its iron-clads, the Department has experimented by the con- 

 struction of different classes and sizes, both in wood and iron, pro- 

 pelled by one screw and by two screws, working independently 

 of each other. In its most recent constructions, of the Miantonomoh 

 class, a wooden vessel designed by the naval constructors, and built 

 at the navy-yards, with Ericsson turrets, and machinery designed by 

 the Bureau of Steam Engineering, a high rate of speed, perfect 

 ventilation, impregnability, and the enormous battery of four 15- 

 inch guns, have been combined in a vessel of the moderate size of 

 1,06-4 tons, drawing only twelve feet of water. These vessels are 

 free from the disadvantage of fouling, which so greately reduces the 

 speed of iron ones. 



Others of this type, but of increased tonnage, arc in process of 

 construction, to have still higher speed, and be adapted to coast 

 service. 



In the steamers bought from the commercial marine of the country, 

 and in the captured blockade runners* now adapted for naval service, 

 are to be found every variety of machinery, both screw and paddle- 

 wheel, constructed either in this country or Great Britain. So far 

 as the exigencies of the war would permit, the different types of 

 machinery have been submitted to careful experiment to ascertain 

 their relative merits. Nearly every variety of boiler and of expansive 

 gear, of rate of expansion, and of saturated and superheated steam, 

 has been made the subject of accurate experiment, and it is believed 

 that the liles of the Department contain the latest and most reliable 

 information on these subjects. 



Nearly all the kinds of coal of the seaboard States have been the 

 subject of careful experiment, with a view to ascertain their compara- 

 tive value for naval purposes. A board of engineers has also experi- 

 mented with petroleum as a substitute for coal in naval steamers. 



As opinion appears to have settled upon the horizontal and the ver- 

 tical tubular boilers, as the only ones proper for naval service, the 

 Department has one of each kind manufactured according to designs 

 furnished by a board of nine engineers, employed in the principal 

 private steam-engine manufacturing establishments of the country, 

 and by the Bureau of Steam Engineering, for the purpose of accurate 

 experiments, to determine their respective merits. These experi- 

 ments will be of the most elaborate nature, and will, it is presumed, 

 enable a choice to be made. They are now in progress. 



A commission of nine, on practical engineering, has been appointed 

 by the Department, consisting of three from the Academy of Science, 

 three from the Franklin Institute, and three on the part of the Depart- 

 ment, all eminent in physical science, to devise the proper appa- 

 ratus, and make the necessary experiments therewith, to ascertain 

 by practical results the economy of using steam with different degrees 

 of expansion. These experiments, which are now in progress, will 

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