44 Mr llussell on tlic Fallacies of the 



from the chambers, which remainder is a large portion of the 

 power withdrawn from useful effect. 



Inventors of Rotatory Steam-Engines of Third Class, See PI. I. 



Figs. (21-30). 

 James Watt, . A. D. 1782. Bryan Donkin, . A. D. 1803. 



Class IV. — Rotatory engines, having a Revolving Piston, are 

 constructed on a much better principle, and hold out much 

 fairer prospects of successful competition with those having the 

 ordinary reciprocating piston, tlian any of the species of the 

 three first classes that have been already considered. In these 

 classes the steam is not confined in rigid vessels, but its action is 

 applied to producing currents in fluids, and force is expended 

 in medial effects which are useles^ and therefore waste power. 

 This is not the case in the steam-engine of the revolving piston. 

 The steam is confined in a close and rigid chamber, and acts 

 only on a solid inflexible surface, and makes its escape by con- 

 fined passages, so that its full effect may be obtained in useful 

 work. Abstractly considered, it is an engine capable of giving 

 out the full power of the steam, and therefore may fairly be 

 imagined to come into competition with the ordinary recipro- 

 cating crank engine. The objections to it are entirely of a 

 practical nature, and regard the engine not in its abstract ma- 

 thematical form, but as a machine made of destructible matter, 

 of matter imperfectly elastic, of surfaces opposing resistance to 

 motion, of matter obeying the known laws of motion and rest. 

 These objections are not the less valid that they are of a sensible 

 and tangible, rather than a speculative description. But as a 

 natural consequence of the more plausible deceptions held out 

 by this species than by any of the three preceding ones, it has 

 followed, that the fallacies of this class have been more widely 

 seductive than any of the others. The Patent-office presents 

 us with the names of more than forty victims, including some 

 of the highest fame. 



Inventors of Rotatory Steam-Engines of the Fourth Class. See 

 PI. I. Figs. 31-80. 



I.James Watt, A. D. 1782 4. Edmund Cartwiight, A.D. 1707 



2. James Cooke, . ... 1787 5- Jonathan Hornblower: ... 1805 



3. Bramah& Dickinson. ...1790 0. William Murdoch. ... 180.") 



