European engineers, where fuel costs are double and triple American fuel costs, have of necessity paid more attention to the subject of steam economy and have outstripped this country in design and use of economical steam engines, notably of the so-called “uniflow,” “drop valve,” “poppet valve,” or “Lentz” type and with the use of superheated steam, have reached much higher efficiencies. The fast increasing costs of fuel in this country have necessitated American builders resorting to high steam pressures with independent or integral superheaters in conjunction with steam boilers, and as a result American manufacturers are offering simple uniflow engines for high speed (say 200 r. p. m.) direct connection to electric generators. Also compound drop valve or poppet valve or Lentz types for slowly moving engines, viz.: 60 r. p. m. for connecting to ammonia compressors and in either case with steam at an initial pressure of 160 lbs. and ordinary superheat of 100° operating condensing, engines of the above types under the conditions named can be readily bought under guarantees to produce an indicated horsepower with the use of 12 lbs. of steam per horsepower hour. The uniflow engine is now offered by several builders and is adaptable to most any service, atmospheric exhaust, condensing or against a back pressure using the exhaust for cooking or heating. There is but little advantage, however, in a uniflow engine under this circumstance unless it be the flexibility as to conditions of operation. =Exhaust Steam.=--The practice of using exhaust steam, that is steam which has passed through engines, for heating and cooking is considered economical. It is based upon the theory that the quantity of heat contained in a pound of steam that has been reduced in pressure from its initial or high pressure, say 100, to a low one--example 5 lbs., and then used for heating, etc., contains almost as many heat units as it did originally. There are many places where this low pressure or exhaust steam can be used advantageously, but if extensively used, the likelihood will be to have long mains into which certain equipment will pass its exhaust and from which the demand will be spasmodic for cooking purposes and intermittent for heating, except during winter seasons, and as a result there is a considerable quantity of steam passed to the air at most times. A careful analysis is necessary for intelligent use of this idea, since the maintaining of a balance owing to business fluctuations and changing seasons makes an almost unmatchable combination. During one season live steam will be used for make up, and at other times there is a surplus. =Advice As To Exhaust Steam.=--Aside from heating feed water and drying where the requirement is constant, a better practice is probably to limit the extent of exhaust steam systems and use live steam for most purposes.