NOTES ON STATIONARY ENGINES. 



41 



itsolf and tlioso connected with it, but also in the general 

 interests of steam-engine practice. As it was, its influence 

 was not inappreciable, as speeds have been slowly but 

 steadily I'ising over since, and probably would not at the 

 present moment have been even at their present pitch but 

 for the Allen engine. Mr. Porter himself will, however, be 

 better I'cmombered in connection with, liis own govei'nor and 

 with Richard's indicator, rather than with the engine. 

 Before leaving the question of higli speed, it may be re- 

 marked that a thorouglily balanced condition all over is 

 essential to the success of such machinery. All revolving 

 parts must be balanced in detail ; in other words, any dis- 

 turbing element must be met by a compensating one, revolv- 

 ing in its own plane. It is not in the least degree sufficient 

 that a standing balance bo insured, as two wrongs cannot 

 malce one I'ight, and I'oally the addition of the second one 

 (so-called balance), aggravates rather than relieves the 

 trouble; this principle is of common application to all 

 machinery in good practice. In steam-engine work another 

 element is introduced, but one which usually does not receive 

 tlu! slightest attention; this is the ba-Ianoing, or rather the 

 adjustment, of tho reciprocating parts. It is commonly 

 assumed that all reciprocating weight is injurious in its 

 effect on the running of an engine, aiid that consequently, if 

 piston rods, pistons, connecting rods, etc., could bo made of 

 sufficient strength and without weight, an important gain 

 would be secured. This may bo true if no expansion of" 

 steam be allowed, but in. iiny other case is a fallacy. In an 

 engine working on a high or moderately high grade of ex- 

 pansion, and with comparatively light recipi'ocating weights, 

 there is a great tendency f(n- the engine to run more quickly 

 durino' the first part of the stroke than it does afterwards. 

 This is in a greater or less degree met by weighting the 



