The most conclusive and most practical evidence that a saving is possible through the use of superheated steam is in the fact that in the largest and most economical plants it is used almost without exception. Regardless of any such evidence, however, there is a deep rooted conviction in the minds of certain engineers that the use of superheated steam will involve operating difficulties which, with additional first cost, will more than offset any fuel saving. There are, of course, conditions under which the installation of superheaters would in no way be advisable. With a poorly designed superheater, no gain would result. In general, it may be stated that in a new plant, properly designed, with a boiler and superheater which will have an efficiency at least as high as a boiler without a superheater, a gain is certain. Such a gain is dependent upon the class of engine and the power plant equipment in general. In determining the advisability of making a superheater installation, all of the factors entering into each individual case should be considered and balanced, with a view to determining the saving in relation to cost, maintenance, depreciation etc. In highly economical plants, where the water consumption for an indicated horse power is low, the gain will be less than would result from the use of superheated steam in less economical plants where the water consumption is higher. It is impossible to make an accurate statement as to the saving possible but, broadly, it may vary from 3 to 5 per cent for 100 degrees of superheat in the large and economical plants using turbines or steam engines, in which there is a large ratio of expansion, to from 10 to 25 per cent for 100 degrees of superheat for the less economical steam motors. Though a properly designed superheater will tend to raise rather than to decrease the boiler efficiency, it does not follow that all superheaters are efficient, for if the gases in passing over the superheater do not follow the path they would ordinarily take in passing over the boiler heating surface, a loss may result. This is noticeably true where part of the gases are passed over the superheater and are allowed to pass over only a part or in some cases none of the boiler heating surface. With moderate degrees of superheat, from 100 to 200 degrees, where the piping is properly installed, there will be no greater operating difficulties than with saturated steam. Engine and turbine builders guarantee satisfactory operation with superheated steam. With high degrees of superheat, say, over 250 degrees, apparatus of a special nature must be used and it is questionable whether the additional care and liability to operating difficulties will offset any fuel saving accomplished. It is well established, however, that the operating difficulties, with the degrees of superheat to which this article is limited, have been entirely overcome.