42 



NOTES ON STATIONARY ENGINES. 



i-eciprocatiBg parts. The mathematical expression of this 

 principle is a very simple one ; it is not however necessary to 

 go into it here, but anyone interested may find it in Porter's 

 book on the " Richard Indicator," in linginecring, and else- 

 where. While on the question of engine-balancing, it may 

 be remarked that great advances in this respect have been 

 made in locomotive practice during the memory of many of 

 those in this room, and this success may bo instanced in dis- 

 proof of the principle just now referred to, viz., that all 

 balancing should be effected in the plane of the disturbing 

 element. In locomotive practice, it must however be re- 

 membered that the balancing is efi'ccted in the wlieels to 

 compensate for the cranks, big ends, etc.; when however 

 the combined effect of the two balances is i-egarded, it is 

 found to fall in the centre of the engine, and consequently 

 the correct principle is followed with a closer degree of 

 approximation than at fir.st appears. This principle of 

 splitting the balance into two equal and opposite pai'ts has 

 often been practised with good results ; one case which may 

 be mentioned is that of Mr. J. Bourne, who designed and 

 introduced a specially good and compact engine aboat 1874, 

 but which failed to take with owners. In this engine 

 another point was tried, and perhaps this might have much 

 to do with the failure ; it was simply the rating of the 

 article by the indicated horse-power, instead of the nominal. 

 This afforded a better comparison with other engines as to 

 the capacity for work, but it was open to the objection that 

 owing to the fact that other makers of small engines did not 

 follow the same custom, many corrections were necessary. 

 It had also a tendency to appear to the ordinary buyer oE 

 small engines to be a thorough imposture. It is however un- 

 necessary to remind the present audience that the rating 

 of marine engines is becoming slowly but surely to be 



