S/R WILLIAM SIEMENS, F.R.S. 45 



The engines of the " Ericsson " are said to consist of four 

 working cylinders of 14 feet diameter and 6 feet stroke, making 

 upwards of 14 strokes per minute. 



. 4 x 21108 x84 x8 



Their collective indicated H.P. is - = 67G, 



00,000 



from which must be deducted 83 per cent, for friction of pistons 

 alone, and say 27 per cent, for friction of general machinery and 

 of the air in rushing through the regenerator ; in all CO per cent., 

 leaving 271 actual horse power. 



There still remains one distinct class of engine for consideration, 

 namely, the combined steam and ether engine. This consists of 

 an ordinary steam engine with a tubular condenser. Instead of 

 the cold water, which is usually admitted into the chamber sur- 

 rounding the tubes, ether, or chloroform, is substituted, which, it 

 is well known, boil at a temperature far below the boiling-point of 

 water, and therefore will generate their own vapours, under a 

 considerable pressure, by the heat given off by the steam in the 

 act of condensation. The vapours of ether, or chloroform, are 

 made to give motion to a second engine, and are in their turn 

 condensed by very cold water. 



It would seem, at first sight, that by this ingenious arrange- 

 ment the power obtained for a given quantity of fuel was doubled, 

 if compared with the performance of the steam engine alone ; 

 but the preceding investigations will have proved, that the heat 

 imparted to the ether must fall short of that given out under the 

 steam boiler, in proportion as the heat is changed into the dynamic 

 effect obtained from the steam engine. The additional effect of 

 the ether engine might indeed be obtained at once from the steam, 

 if the expansive action of the steam was sufficiently extended ; 

 considering, however, that an engine, in which the steam is ex- 

 panded at one- third part of the stroke, absorbs only about one- 

 eighth portion of the entire heat of the steam, and considering 

 also that it is very inconvenient to extend the rate of expansion 

 much further, in rotary engines, there remains, at present, a 

 considerable advantage in favour of the combined steam and ether 

 engine, if the practical difficulties involved, such as the tightness 

 of the joints, are not taken into account. Supposing the dynamic 

 equivalent, per unit of heat obtained by the engine, to be 

 90 foot-lbs., that of the ether engine may be taken at two-thirds, 



