EXPLANATION OF THE PLATES. 3.59 



PLATE XXXI. 



This plate is a longitudinal section of the preceding engine with boiler attached, 

 and the same reference letters apply to both. 



The engines and boiler stand on sleepers of oak X X, African oak from its stiffness 

 being generally employed. And the base of the engine is secured by bolts passing 

 through the sleepers and bottom timbers 1 . The steam pipe S brings the steam from 

 the boiler to the space between the slides, c, and by their movement admits it to top 

 and bottom of cylinder A. At the termination of each stroke it passes to the con- 

 denser B, by the upper and lower eduction pipes, C and D, and is there condensed 

 by a jet of cold water. The air pump E, withdraws the air and water, from the 

 condenser to the hot-water cistern F, which being close at the top forms an air 

 vessel to expel the water from the cistern through the waste water stop- valve pipe G. 



The motion of the piston rod is transmitted to the crank by means of the main levers 

 H, I, moving on the main gudgeon K. These are connected at the cylinder and to 

 the cross bar of the piston by two side rods L L, and the other end, 1 1, to the crank 

 by the connecting rod M. 



The air pump E is also worked by two side rods from the main levers, and the 

 hot water and bilge pumps from the same air-pump cross bar N. 



The piston rod is guided by a parallel motion a a, the slides b b are separate, but 

 connected by a rod similar to their land construction of 1808. These and the upper 

 eduction pipe have been lately applied by Boulton and Watt, and may be considered 

 a great improvement upon the long slide, where the expansion of the metal is liable 

 to twist the face and render them leaky. 



Motion is given to the slide valves by the eccentric circle 0, by means of the ec- 

 centric rod d, connected with the eccentric arm e, from which it may be disengaged 

 with facility when the engines are required to be stopped ; /, the working gear shaft, 

 receiving its action from the eccentric arm. 



P P, Upper and lower blow valves, the former is used before starting the engines 

 to admit steam into the condenser to blow out the air and water by the lower valve, 

 so as to form a partial vacuum in the condenser. 



Q and R, Upper and lower headstock frames which support the engine and paddle 



1 It may not be irrelevant to notice here, that owing to this mode of securing the engines the pro- 

 prietors of the Red Rover were recently enabled to raise that vessel when sunk in forty feet water. 

 The principal chain which lifted her being secured to the frames of the engines, it having given way 

 when fastened to the vessel itself. It is the practice of some makers to bolt only through the sleepers, 

 which we by no means consider so secure. 



