390 EXPLANATION OF THE PLATES. 



PLATE LV. A. 



This plate represents a longitudinal section of Mr. Francis Humphrys's patent 

 marine engine, of fifty horses' power, as executed by the Messrs. Hall, of Dartford. 



A A, Is the cylinder. 



B B, The working piston. 



C, The crank. 



D D, A steam-tight casing or trunk, of a rectangular form, rounded at each end, 

 which is permanently attached to the piston in such manner that the axis of the 

 one shall correspond exactly with that of the other, and which works up and 

 down with the piston, 



E E, Is the lid or cover of the cylinder A A. 



G G, The stuffing box, which is made to fit the outside of the casing or trunk 

 D D, instead of, as usual, fitting the piston-rod. 



H, Is the connecting rod firmly secured to a cross pin or axis I, working in 

 metallic bearings, one end of which rod is attached to the bottom of the piston, 

 and the other passes up through an aperture in the piston into the casing or 

 trunk D D, and is ultimately connected with the crank C. 



K K, Is a box or cover which encloses the cross-pin or axis I, with its bearings, 

 and is jointed steam tight to the piston. 



L L, A hollow space cast in the cylinder bottom or bed-plate for the reception 

 of the box K K, when the piston is at the bottom of the cylinder. The 

 result of these arrangements is, that on the engine being set to work the motion 

 of the piston is at once communicated by the connecting rod H, to the crank 

 C, and causes it to revolve without the intervention of beams, cross-heads, 

 or other auxiliary appendages, by which diminution in the number of the 

 moving parts of the engine, and consequent simplification of its action, it is 

 greatly reduced in size and weight. 



a a, Slide valves. 



c, Starting handle. 



d, Air-pump rod. 



f, Discharge pipe. 



g, Snifting valve. 

 h, Eccentric rod. 



e, Hot well. 



The same letters of reference are employed to denote the same parts of the engine 

 in each of the engravings, by a reference to which its operation will be better under- 

 stood. 



