EXPLANATION OF THE PLATES. 
390 
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. 
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. 
f Discharge pipe. 
cj, Snifting valve. 
h, Eccentric rod. 
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