42 Mr Russell on the Fallacies of the 



Class II. — Rotatory engines of Medial Effect are those which 

 do not immediately give revolution to an axis by the action of 

 steam upon the wheel, but have a medium of communication 

 between the power and the effect, which medium is the direct 

 agent in circular motion. This class of engines will be well 

 understood by taking as its type any simple steam machine, 

 such as Savary's and Newcomen's, used for raising water, 

 which water by falling on the floats of a common mill-wheel 

 will then give rotatory motion to it. The engine of Savary 

 raises water by pressing directly on its surface, and it is only 

 necessary to allow this water to fall on a wheel, when it will be 

 made to revolve and form an engine of the 2d class. 



A variety of this class has been invented of which the fire- 

 wheel of Amontons is a type. The stream pushes water through 

 certain channels that form the arms of the wheel, from a set of 

 chambers on one side of the wheel, to a corresponding set of 

 chambers on the opposite ; and thus the side filled with water 

 preponderates over the other, and the wheel revolves. The 

 water being constantly driven off by the steam from a given 

 side of the wheel to that opposite, uniform revolution is the re- 

 sult of the weight of the water. In this state, although steam 

 is the agent, water is the medium of communicating the rota- 

 tory motion. See Plate I. Fig. 11. 



Solids have also been made the medium of effecting rotation 

 in this manner ; weights of solid mater, in the form of pistons, 

 have been transferred by the force of steam to a considerable 

 distance from the centre on one side of a wheel, and drawn 

 nearer to it on the other side, so as, by bringing about a con- 

 tinual preponderance on one side, to effect revolution. Watt 

 and Witty have designed rotative mechanism of this nature. 



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

 PI. I. Figs. 11-20. 



1. Guillaume Amontons, A. D. 1699 6. Richard Witty, A. D. 1810 



2. Leopold of PlainiU , ... 1723 7. Sir W. Congreve, ... 1818 



3. Cliampion of Bristol, ... 1752 8. John Moore, . ... 1820 



4. James Watt, . ... 1769 9. Sir W. Congreve, ... 1821 



5. Davidson &Hawkesley, ... 1793 1 0. Thomas Masterman, ... 1822 



In this class of engines the loss of effect is manifest, for it is 

 necessary that the steam, in order to produce circular motion, 



