dragged two laden sloops of seventy tons burden each, the Active and Euphemia, a distance of 19 miles in six hours, against a strong adverse gale.

His experiments were here ended, through the fear of the managers of the canal that its banks might be injured by the undulation caused by the wheels.

the Hudson.

In 1811, Mr. Bell's first boat, the Comet, was tried, and set to work on the Clyde. Mr. Bell, as well as Mr. Fulton, had been on board of Mr. Symington's boats, and satisfied himself of their efficiency.

Having thus taken a rapid glance at the main points of interest in connection with the history of steam-boat navigation, we proceed to illustrate the various kinds of modern marine engines. These are of two kinds— engines as applicable to the driving of paddle-wheel steamers, and those applicable to " screw" steamers.

The engines adapted for paddle-wheel steamers are of two kinds, " sidelever" and "direct-action." The arrangements of the ordinary side-lever engine will be understood from an inspection of the drawing in fig. 162. As will be observed, this is a modification of the land beam-engine; but as the space overhead in all steam-boats is necessarily limited, the beams are arranged at the lower part of the engine. The cylinder is at a a, b b the working beam, c the steam-pipe, d d the side-rod connecting the end of the beam with the cross-head of the piston rod e, f the parallel motion; g the connecting-rod connecting end of beam with crank h, 1 paddle-shaft, m eccentric-rod, n o p starting handle and valve gearing; rr condenser airpump, worked by the side-lever connected with beam and cross-head of air-pump piston-rod, s s air-vessel, tt framing.

The drawing in fig. 38 shows the arrangement Mr. M'Naught adopts in his double-cylinder marine engines.

In fig. 163 we give a diagram illustrative of the connection of cylinder, condenser, and air-pump. a is the cylinder, b the piston-rod, c the lower, d the upper steam port, e the passage leading to the condenser f. A division is placed between the condenser and the eduction passage e, to prevent the injection-water passing to the lower part c of the cylinder. g the air-pump, hi the air-vessel. We now give descriptions of a few of the details of the engine worth notice. In the air-pump a valve is provided at the bottom plate opening upwards; this is to allow the water to pass from the condenser to the air-pump, but to prevent its return. Another valve is placed at the entrance to the hot-well h (fig. 163); this retaining the

water in the cone, frees the air-pump bucket from an unnecessary weight of water. The air-cone is now frequently dispensed with. Two orifices

are made in the hot-well h, fig. 163, one larger than the other; the small one communicates with the force-pump for supplying the boiler, the other with the sea, and is termed the waste-pipe.

Escape-valves are provided to the steam cylinder; the office of these is to allow a passage to the water which collects above and below the piston. The escape-valve at the bottom of cylinder is weighted with a pressure above that of the steam in the boiler; if this precaution were not taken, the steam a would blow through them on being admitted to the cylinder. The upper escape-valve is generally placed in the cylinder cover, and is retained by a spring in some instances. In some engines the escape-valves are applied to the ports of the cylinder and kept closed with springs.

The diagram in fig. 164 illustrates the method adopted in side-lever engines in working the slide-valves; fis the end of the cross-head of the

valve-rod, ee side-lever, connected with the end d of the rocking-shaft a oscillating on the centre b, and which is moved alternately up and down by the eccentric lever c, to which the eccentric-rod is attached. g is the back balance-weight; the office of this weight is to balance the slide-valve in such a position that both of the steam-ports are closed when the engine is at rest. In starting the engine the rocking-shaft is moved by hand through the agency of a lever attached to it. In place of a lever, many engines have wheels placed vertically, like the steering wheels of ships. The best starting gear is that known as Stephenson's link motion, used in locomotives, and which, in Chapter V., we have illustrated and described. This also forms the best reversing gear, as by it the full speed a-head can be instantly changed for full speed a-stern without stopping the engines. In engines where this contrivance is not used, the eccentric has to be thrown out of gear before the engine can be reversed. On the crank-shaft, on which the eccentric is placed, a snug or projection is made, as at b, fig. 165; two snugs are also fitted, as at cd. Suppose the shaft revolves so as to bring the face ƒ of the snug b against the snug c, the eccentric moves in the direction of the arrow; but if it is desired to change the motion, the shaft a revolves in the contrary direction, and the face e of the snug b comes in contact with the snug d.

The comparatively large space occupied by side-lever engines, has directed the attention of many of our engineers to devise arrangements by

which space would be economised. This has been attempted, and in some instances with considerable success, by the introduction of the direct-action engine. The varieties of this class are very numerous. To the reader anxious to have a knowledge of these, we must refer to larger works; the Artisan treatise gives many illustrations under this head. Our space permits us only to give some simple diagrams illustrative of the most noted of these. The distinguishing feature in this form of engine is the absence of the side beams, rotatory motion being given at once to the paddle-shaft from the piston-rod. In fig. 166 we give a diagram illustrative of the

"steeple-engine," much used in the Clyde. a is the piston-rod, carrying a triangular cross-head bb; c the paddle-shaft, d the connecting-rod, attached at one end to the upper extremity of the cross-head bb; and the parallelism of the piston-rod is maintained by the guide e, in which the cross-head m works.

In fig. 167 we illustrate the arrangement of the Siamese or double

ee the piston-rods connected with the cross-head ee, which is continued downwards to d, and which slides between the two parallel guides e; one

end of the connecting-rod is attached to e, and the other to the crank g, on pedestal f. In fig. 168 we give a diagram illustrative of another form of direct-acting engine, which is considered as exceedingly compact; "indeed," says an authority, "no engine can occupy less room than this; for its length is little more than the diameter of the cylinder." Let a represent the piston-rod, b the connecting-rod, cc the paddle-shaft, d the air-pump rod worked by an eccentric on the shaft cc. The cylinder-valve is worked by the eccentric-rod f, fig. 169, from an eccentric on shaft cc fig. 168; the rod ƒ works the levers a and valve-rod g; h the pedestal fixed to the pillar e; m is the eccentric-rod working the air-pump rod n corresponding to d, fig. 168. In direct-action engines, where the connecting-rod is between the piston and the crank, the engine is designated as belonging to the class known as the "Gorgon engine," introduced by Messrs. Seaward, where the connecting-rod is above the crank a; they come under the designation of steeple-engines.

A well known form of direct-action engine is that known as the "oscillating." We have already described the action of this; we now give a diagram showing its application to a paddle-wheel steamer (fig. 170).

fig. 170.

Where vessels are propelled by the "screw," engines differing in arrangement from those we have already described are adopted. The screw having to make so many more revolutions than paddles in the same space of time, the speed of the screw-shaft is sometimes brought up by cogwheels. In the engines of the Great Britain this arrangement is adopted;