378

MODERN STEAM PRACTICE.

wheel vessel built, was fitted with a pair of side-lever engines, thediameter of cylinders being ioo inches, with a stroke of 12 feet.The diameter of paddle wheels was 40 feet.

A specimen of the early side-lever engine may still be seen placedon a pedestal at Dumbarton pier on the Clyde. It is the first marineengine made in 1824 by Mr. Robert Napier, the well-known Clydeengineer, for the Steamer Leven.

Trunk engines were introduced by Penn, and have been muchused in H.M. navy. The piston rod is made hollow, and the connect-ing rod being centered well down in it a saving of room is effected.

A form of engine now common on Clyde river Steamers is thediagonal direct-aciing. In these engines the piston rod is attachedto a crosshead working in slides, and from this crosshead the con-necting rod Stretches to the crank pin. It may be of interest hereto state that the first efficiently steam-propelled vessel, the Char-lotte Dundas, was fitted with a horizontal direct-acting engine; thisvessel was tried successfully on the Forth and Clyde Canal in 1802.

In many of the earlier steam vessels, from the Comet downwards,spur-wheel gearing was used to connect the engine with the paddleshaft. A few details of the size of the Comet may be interesting.She was about 25 tons bürden, and was built for Henry Bell in 1812by Mr. John Wood of Port-Glasgow. She measured 42 feet long,40 feet keel, and 11 feet broad, with 5 feet 6 in. draft of water.The engine, made by John Robertson of Glasgow, was a condensingone of 3 horse-power, the diameter of cylinder being 11 inches, andthe stroke 16 inches, the crank working below the cylinder; theengine-shaft, connected with a fly-wheel, is said to have been otcast-iron, and 3 in. square. The engine was fitted on board beforelaunching and steam raised. At first the Comet was fitted withtwo pairs of paddles, 7 feet diameter, with spur-wheels of 3j4 feetdiameter; but soon afterwards she was lengthened to 60 feet, anda new engine with a single pair of paddles substituted, the speedbeing now greatly improved, and reaching from five to six miles anhour. The diameter of the cylinder is stated as I2j£ inches andthe horse-power 4.

THE PADDLE WHEEL.

The paddle wheels now in use are generally of the feathering type,the floats entering and leaving the water almost vertically; having thusa better hold of the water than the fixed floats, which enter obliquely,