32 ANNUAL OF SCIENTIFIC DISCOVERY. 



from 40 pounds to 50 pounds per square inch, and worked with 

 but little expansion, have in certain cases showed more econom- 

 ical results when worked with a mixture of steam and air than 

 when worked with steam alone in the ordinary way. But we 

 submit that such engines although we regret to say that large 

 numbers of them exist are not fair examples of steam machin- 

 ery, and that the credit to be derived from beating them in econ- 

 omy is but very small. Given an engine consuming say 8 pounds 

 or 10 pounds of coal per indicated horse-power per hour, and the 

 difficulty of making such alterations as will produce a more 

 economical result is not great. If the aero-steam engine is to 

 take a high position in the future, it must do far more than this ; 

 it must be proved to be more economical both as regards fuel and 

 maintenance than steam engines of thoroughly good construction, 

 such as are turned out by our leading makers ; and at present we 

 have but small hope that any such proof will be forthcoming. In 

 making this assertion, we have no wish to discourage Mr. War- 

 sop, Mr. Parker, or others, who, like them, are experimenting 

 on the use of steam and air in combination ; but what we desire 

 to point out is, that they would save themselves much use- 

 less present labor and expense, and future disappointment, if, 

 instead of contenting themselves with beating indifferent steam 

 engines, they would ascertain carefully and without prejudice 

 just what their respective systems can or cannot effect under the 

 best condition under which they can be applied. Engineers well 

 know that for a certain sum of money a steam engine can be con- 

 structed to develop a certain power with a certain consumption 

 of fuel. Let it be proved that by the adoption of the "aero- 

 steam " system there can be constructed for the same sum an 

 engine developing a greater power with the same consumption 

 of fuel, or the same power with a less consumption of fuel, and 

 without any increased cost for maintenance, and the value of 

 mixed steam and air engines will be established. Scientific 

 American. 



THE FRICTION OF STEAM ENGINES. 



If we did not believe that it is easy to say something new on a 

 subject which has been in a very peculiar sense worn threadbare 

 by the inventors of cylinder lubricators and steam greasers, this 

 article would never have been written. So far as we are aware, 

 all the information regarding the resistance of steam engines due 

 to friction is to be found in the circulars of inventors, one or two 

 papers read before engineering societies by the advocates of par- 

 ticular methods of lubricating engines, certain theoretical disqui- 

 sitions contained in text-books of mechanical science, and perhaps 

 a report or two in the "Journal of the Royal Agricultural 

 Society." It is almost needless to say that the subject is one of 

 very considerable importance ; but it may be worth while to bring 

 this importance home in a tangible form to the employer of steam 

 power. It may be stated, in pursuance of this object, that it by 

 no means follows "that an engine giving a very high indicated 



