Be PORT OF Superintendent. 75 



theoretical rules should have used less steam and fuel. (See lines j)- 

 and </., table 2.) The tact that this engine did not use less weight 

 of steam, corresponds with the known wet condition of the steam, as 

 mentioned hereafter. 



Tlie trial between the Babcock and Wilcox and Harris engines 

 possesses considerable scientific interest, from the fact that the cylinder 

 of the former was steam jacketed while that of the latter was made 

 direct from the Corliss patterns and Mdthout jacket. 



The jacketed cylinder of the first named engine was surrounded 

 by an air jacket, having a polished external covering. The Harris 

 cylinder was clothed with felt, under a wood casing with the excep- 

 tion of the steam chests which were exposed and polished. The 

 engines were of the same size, and as they were run also at the same 

 speed the results are in every respect comparable. 



The economy of these two engines is very remarkable. The best 

 result possiljle by theory, for an engine woi-king under the circum- 

 stances of this trial, is twenty-one pounds of water per indicated 

 horse power per hour, and both engines approached this limit very 

 closely. 



To make this report complete, it is necessary to call attention also 

 to certain prominent facts connected with the construction and man- 

 agement of the two engines. 



The Corliss engine, built l)y Mr. Harris, was erected on a heavy, 

 full length, deep laid foundation, was carefully finished and put in 

 line and operated faultlessly, showing great mechanical ability in its 

 manufacturer. The Ba1)cock and Wilcox engine was erected on brick 

 piers, and water accidentally got into the wheel pit and loosened 

 this foundation, so that the engine moved considerably at every 

 stroke. 



After tlie trial, upon examination of the Babcock and Wilcox 

 engine, it was found that, on account of a defect in the cylinder 

 casting, the outer division of the valve face was too narrow by one- 

 fourth of an incli, to cover the opening in the main valve. This 

 defect admitted steam to the cylinder during the latter part of the 

 expansion portion of the stroke, causing a prominent protuberance on 

 the indicator diagram. 



Tlie steam supplied to the Babcock and Wilcox engine was quite 

 wet during much of the time, as was observed particularly by one of 

 the judges and other persons present. This can only be accounted 

 for by the same difi:erences in firing, or in operating the fire doors, 



