ADDRESS. 21 



absolute temperature x could be raised to that of combustion, and t' 

 reduced to atmospheric temperaturOj and these maximum limits can bo 

 much more nearly approached in the gas engine, worked by a combustible 

 mixture of air and hydro-carbons, than in the steam engine. 



Assuming, then, in an explosive gas engine a temperature of 1,500° C. 

 at a pressure of 4 atmospheres, we should, in accordance with the second 

 law of thermo-dynamics, find a temperature after expansion to atmospheric 

 pressure of 600° C, and therefore a working range of 1500° - 600°= 900°, 



and a theoretical efficiency of ' — — — = about one-half, contrasting 



very favourably with that of a good expansive condensing steam engine, 



in which the range is 150 — 30 = 120° C, and the efSciency " ^ =^- 



A good expansive steam engine is therefore capable of yielding as 

 mechanical work -f th parts of the heat communicated to the boiler, which 

 does not include the heat lost by imperfect combustion and that 

 carried away in the chimney. Adding to these the losses by friction and 

 radiation in the engine, we find that the best steam engine yet con- 

 structed does not yield in mechanical efi'ect more than |th part of the 

 heat energy residing in the fuel consumed. In the gas engine we have 

 also to make reductions from the theoretical efiiciency, on account of the 

 rather serious loss of heat by absorption into the working cylinder, which 

 has to be cooled artificially in order to keep its temperature down to a 

 point at which lubrication is possible ; this, together with frictional loss, 

 cannot be taken at less than one-half, and reduces the factor of efficiency 

 of the engine to jth. 



It follows from these considerations that the gas or caloric engine 

 combines the conditions most favourable to the attainment of maximum 

 results, and it may reasonably be supposed that the difficulties still in 

 the way of their application on a large scale will gradually be removed. 

 Before many years have elapsed we shall find in our factories and on 

 board our ships engines with a fuel consumption not exceeding 1 pound 

 of coal per eSective horse power per hour, in which the gas producer takes 

 the place of the somewhat complex and dangerous steam boiler. The 

 advent of such an engine and of the dynamo-machine must mark a new 

 era of material progress at least equal to that produced by the intro- 

 duction of steam power in the early part of our century. Let us con- 

 sider what would be the probable eSect of such an engine upon that most 

 important interest of this country — the merchant navy. 



According to returns kindly furnished me by the Board of Trade and 

 ' Lloyds' Register of Shipping,' the total value of the merchant shipping 

 of the United Kingdom may be estimated at 126,000,000^., of which 

 90,000,000^. represent steamers having a net tonnage of 3,003,988 tons ; 

 and 36,000,000^. sailing vessels, of 3,688,008 tons. The safety of this vast 

 g,mount of shipping, car:ryiDg about five-sevenths of our total impprts 



