DOMESTIC MOTORS. 487 



proach the limit of economy as closely as it is possible to do. It is the 

 invention of M. Simon, and was first brought to extended public no- 

 tice at the Paris Exposition of 1878, where it was exhibited in sizes of 

 from one to four horse. A diluted mixture of air and gas is used, as 

 in the Otto, but the compression is done not in the power but in a sepa- 

 rate cylinder. It is admitted to the cylinder by a slide-valve of simi- 

 lar construction to that of the Otto, but the manner of using it differs 

 materially from that employed in the latter machine. In the Otto 

 the entire combustible charge is introduced into the cylinder before 

 ignition takes place, and, though the proportion of air is such that the 

 combustion is not an explosive one, still it is completed within a time 

 that covers but a small fraction of the stroke. In the Simon, on the 

 other hand, the combustible mixture is introduced in small quantities 

 that are successively inflamed, producing a gradual expansion of the 

 gases that, along with the steam also admitted, exert a pressure upon 

 the piston more nearly like that in the steam-engine than is attained 

 in any other machine. The ignition is accomplished by a jet always 

 lit, placed just inside of several thicknesses of wire gauze, to prevent 

 the flame retreating into the combustible mixture without the cylinder. 

 The water that is afterward admitted to the cylinder is first used to 

 jacket it, and thus becomes slightly warm. From the jacket it is passed 

 into a steam generator, where a portion of it is vaporized by the heat 

 of the exhaust-gases. This steam is then admitted into the cylinder 

 along with the combustible charge, and further heated and expanded 

 by the ignition of the latter. The water in the steam generator circu- 

 lates through the jackets of both the compression and power cylinders, 

 first taking heat from the compression cylinder, then from the power 

 cylinder, and reaching the generator quite warm. The heat is there- 

 fore utilized to the utmost, and as a consequence the economical result 

 is superior to any before attained. According to M. Simon, the con- 

 sumption of gas is a little less than eighteen feet an hour per horse- 

 power. The motor occupies a little larger floor-space than the Otto, 

 though it is of less weight, and is somewhat higher in price. 



Either of these engines could doubtless be made in sizes small 

 enough to drive simply a sewing-machine or a scroll-saw, though prob- 

 ably not at prices that would allow of their extended use. Only one 

 gas-engine appears to have been so far made of such small power 

 that invented by M. de Bisschof, and shown in Fig. 14. It is much 

 simpler than the above engines, but is also a much less perfect ma- 

 chine, though sufficiently economical for the use for which it is de- 

 signed. The ordinary machine is about one man-power, and is fur- 

 nished at something over a hundred dollars ; a larger one of four 

 times the power costing a hundred and ninety. It is compact, orna- 

 mental in design, and runs smoothly. No oiling is required, and, once 

 started, it may therefore be left to itself for a considerable time. One 

 of them, indeed, is reported to have run for forty-seven days without 



