Rotatory Steam-Engine. 63 



We have thus endeavoured to expose the nature of the fal- 

 lacy under which they labour, who imagine that the present 

 steam-engine, as derived from Watt, is a machine which 

 " destroys" or " absorbs" a large portion of the power it is 

 designed to transmit, and who look to the rotatory engines as 

 a means of increasing the amount of the power given out in 

 useful effect. That the rotatory engines, which appear day 

 after day, are not new, we shew from the fact, that the five 

 great classes which comprehend them all have been invented 

 and re-invented by upwards of ninety individuals. That their 

 inventions have been unsuccessful, is manifest from the non- 

 existence of their machines in the daily use of ordinary manu- 

 factures. That the failures of these contrivances did not 

 arise from defects accidental to the peculiar arrangements and 

 contrivances of the engines, is rendered probable by the great 

 variety of forms in which they have been re-invented, tried, 

 and abandoned. That they have not failed from deficiencies 

 in the workmanship and practical details, is rendered still more 

 probable by the circumstance of finding among the names of 

 inventors, those of the most eminent practical engineers. We 

 have next shewn, that in theory, the crank of the steam-engine 

 in common use, cannot, as has been supposed, be attended 

 with a loss of power, as such loss would oppose the established 

 doctrines of virtual velocities ; it is shewn also from very 

 simple and elementary considerations, that what appears to be 

 lost in force, is resumed in velocity — that, in proportion as the 

 mean force on the piston is greater than the mean force on the 

 crank, in that proportion is the space described by the latter 

 greater than the space described by the former. That the 

 dynamical effect produced in a given time is exactly in the 

 proportion of the steam expended in that given time ; and 

 thus have we arrived at the conclusion, that the common recip- 

 rocating crank steam-engine, has not the favdts attributed to 

 it in theory, and which the rotatory engines have been de- 

 signed to remedy. We have next taken the practical view of 

 the subject — in simplicity of parts the rotatory piston has no 

 advantage over the reciprocating piston ; in difficulty of con- 

 struction the rotatory piston far exceeds the reciprocating en- 

 gine — it is more expensive at the outset — it has more friction 

 — it is more bulky, and less compact — it is inferior in precision 



