Rotatory Steam- Engine. 59 



a very small allowance for friction, the piston gives out through 

 the crank, in actual work done, all the power of all the steam ap- 

 plied to it in the cylinder. Mechanism can do no more.* And 

 since neither simplicity of action, compactness of form, conden- 

 sation of bulk, nor economy, either in first cost or operation, 

 give it a superiority to the common engine, but that, on the 

 other hand, from the very nature of its movement, it possesses 

 the elements of rapid detrition and unequal deterioration, and 

 is, by the necessary arrangement of its parts, rendered pecu- 

 liarly inapplicable to such important objects as the purposes of 

 steam navigation and land transport, I do not see what mo- 

 tive can possibly remain for devoting a single thought to its 

 further improvement, or the alteration of its form, when its very 

 principle holds out no higher premium than that,^if brought to 

 its utmost perfection, it might possibly approach in durability 

 and efficiency the ordinary reciprocating engine, but in no point 

 of view could ever excel it. To expend more time and mind on 

 such a subject, is therefore merely sowing the wind to reap the 

 \yhirlwind. 



VIII. The force of the exposure I have now been induced to 

 make of the fallacious nature of those attractions by which the 

 rotatory motion has drawn aside ingenious mechanists from the 

 direct path of legitimate invention into the fruitless pursuit after 

 ingenious trifles, will have considerable weight added to it, if 

 we turn our attention to the peculiarities of the crank as one of 

 the elementary machines for the conversion of reciprocating 

 into rotatory action. 



The crank, as the means of converting the reciprocation of 

 the piston of a steam-engine into continuous rotatory action, 

 possesses singular and beautiful properties, which distinguish 



" We have before us the printed reports of last year, in which the duty 

 done by the crank engines of Charlestown and Wheel Kitty constructed by 

 Mr Sims is given. We have also before us the indications of pressure in the 

 cylinder, as obtained by a very accurate indicator applied in the course of last 

 summer by Mr Smith of Manchester, who visited the mines for that purpose, 

 and has been kind enough to favour us with a copy of his observations. We 

 have thus the means of comparing the power actually exerted on the piston 

 with the work done, and find the result of the comparison to be, that the work 

 done is within ten per cent, of being perfectly equal to the power employed. Mere, 

 then, we arrive at this conclusion, that the utmost conceivable reach of 

 improvement in the mechanism engine, if it attained even to j)erfection, 

 would not save more than a few ])er cents. That the crank engine there- 

 fore, as at present used, is as near the perfection of mechanism as any thing 

 we can hope to obtain, is, we think, satisfactorily established. 



