that obtained simply by the use of superheated low pressure steam. With the 

 increase in the pressure there was an increase in the temperature and where 

 attempts were made to superheat the high pressure steam to the same degree as 

 had been the practice with the low pressure steam, great difficulty was experienced 

 in lubrication, the present mineral cylinder oils being then unknown, and in some 

 cases the designs being unsuitable for superheated steam. Where superheaters 

 were used it was found necessary to reduce the amount of superheat to a point 

 where its gain was too small to warrant the expense of a superheater installation. 

 The almost universal use of compound engines in marine practice thus made the 

 adoption of superheaters impracticable. Although superheaters had never been 

 as extensively used in stationary work, they were abandoned on land at the same 

 time as at sea. Dr. Kirk introduced the triple expansion engine in 1874 and by 

 1 88 1 it had become the normal type of marine engine, and the still further increase 

 in steam pressure for this type of engine was an additional factor militating against 

 the use of superheaters. 



It is interesting to note that the British Board of Trade took a strong stand 

 against the use of superheated steam on the ground that there was danger of the 

 steam being broken into its constituent elements at high temperatures, and 

 becoming dangerous. This stand, while wholly in error, had an effect in retarding 

 development. 



The use of mineral oils became general in the early seventies (though our 

 present day heavy cylinder oils were unknown) and its use might have furnished 

 the solution of the lubrication difficulties arising from the use of superheated 

 steam had it not been for the fact that the foremost engineers were devoting their 

 whole attention to the increase in efficiency of engines from the use of higher 

 pressures, compounding, and improvements in mechanical details of valve gears, 

 governors, and the like. Superheated steam through this period seems to have 

 been almost entirely forgotten or discarded because of bad reports. A. E. Seaton, 

 in "A Manual of Marine Engineering" (1883), says: "The use of superheated 

 steam has been discontinued since the pressure has gone beyond 60 pounds per 

 square inch, partly in consequence of the increase in temperature beyond that due 

 to the pressure being prejudicial to the good working of certain parts, partly also 

 due to the danger and inconvenience of the superheater itself, and not a little to 

 the action taken by the Board of Trade (British) with respect to it." This 

 statement was made in editions of Seaton's manual as late as 1890. 



There were certain engineers who continued to investigate and experiment 

 with superheated steam through the period when the general interest in the 

 subject was apparently lost. Hirn, his successor, Schwoerer, Schroter, and 

 William Schmidt were pioneers in this second movement toward the introduction 

 of superheated steam. Hirn, in 1892, acting for the Alsatian Society of Steam 

 Users, in an extended series of tests on a large number of engines, showed a 

 saving in coal of 20 per cent for superheaters installed integral with a boiler and 

 12 per cent where the superheaters were independently fired. He used steam 



