1893; 



on Economies in the Utilisation of Energy. 



89 



may have something to do with the pressure of severe competition — 

 are going to do their best to move forward a little, to make larger 

 and faster running machines, and, in fact, to make an effort to pene- 

 trate further into the country where the steam engine has for so 

 long held undisputed sway. About this we must not concern 

 ourselves here, however. The maximum theoretical efficiency of a 

 gas engine is about 80 per cent., or nearly three times as great as in 

 a steam engine. It is obvious that this figure is so high that we 

 need hardly attempt to raise it, 

 especially as we are so far from 

 actually realising it as yet. In 

 Fig. 4 the theoretical maximum 

 efficiency is taken as 100 per cent., 

 in the same way as in Fig. 2, and 

 the line b shows how much of this 

 is actually turned into work, the 

 area above b representing the lost 

 energy. The greatest cause of loss, 

 that above the line c, is represented 

 by the heat taken from the water 

 surrounding the cylinder. The fact 

 is that we are trying to obtain incom- 

 patible results. To reach the high 

 efficiency we make the initial tem- 

 perature very high. But, then, any 

 such temperature would melt up our 

 machines altogether, if the metal 

 were only allowed to reach it. We 

 have, therefore, to adopt the some- 

 what barbarous expedient of con- 

 tinually keeping the metal cool by 

 a current of water passing through 

 a jacket. This water must of neces- 

 sity pick up all the heat which can 

 get through the metal and carry it 

 away to waste. Although, therefore, 

 our theoretical maximum efficiency 

 is so much greater than that of a 

 steam engine, our actual efficiency 

 is not nearly so great (comparing 

 the lines c in Fig. 2 and b in Fig. 4). 

 Notwithstanding this, the actual 

 energy utilised per thermal unit of 



combustion heat in a gas engine is very considerably greater than in 

 a steam engine. Undoubtedly, very great possibilities for increased 

 economies exist here. 



I have reserved to the end some discussion of possibilities and 



