MECHANICS AND USEFUL ARTS. 31 



a cupola for iron and brass casting. The ship's engine and a ten-horse port- 

 able engine supply the necessary power for driving the tools. 



Improved Rudder. In an improvement recently patented by J. S. Robbins 

 of San Francisco, two rudders are employed to steer the vessel. One of 

 them is attached to the stern-post in the usual manner ; the other placed 

 directly behind the first, and secured in an iron frame which projects back for 

 that purpose. The two are connected together with arms hi such a manner 

 that the force of the water, when it comes in contact with the after rudder, 

 will assist the helmsman in moving the post rudder, so that they counter- 

 balance each other. This it is said reduces the labor of steering to almost 

 nothing, gives complete steadiness to the wheel, and enables a single man, or 

 even a boy, to guide the largest vessel in the fiercest storm, with perfect 

 ease. 



India Rubier Lining for Vessels. A plan has been patented by Mr. Y. P. 

 Corbett, of New York, for lining vessels with a continuous coating of India 

 rubber, as a safeguard against leakage. It is intended to apply the lining 

 within the frame of the ship, and beneath the ceiling. A large proportion of 

 the accidents that occur to the hulls of vessels are from striking the bottom 

 in such a manner as not to actually displace, or rather destroy, any portion, 

 but only to strain and split the wood. The whole reliance being on the 

 integrity of the exterior shell, it follows that the starting of a few planks 

 creates a furious leak, and unless the pumps are capable of controlling the 

 evil, the ship is lost. With a gum lining, however, the leak would merely 

 fill the spaces between the frames, and the interior of the hold would remain 

 as dry as before. The edges of the sheets, which are proposed to be from \ 

 to f of an inch in thickness, are to be cemented by heat ; and the gum, it is 

 believed will be as durable as the wood itself. 



A patent for improvement in propellers was granted Chas. de Bergue of 

 London, June 9th. In this improvement the propeller somewhat resembles 

 a rocking arm or blade, working in a chamber open at each extremity, one on 

 each side of the vessel, as a substitute for, and in the place of, the common 

 paddle-wheel It is connected by a rod to a crank on the extremity of the 

 main shaft of the engine, and it thus receives a vibrating treading motion, the 

 action being somewhat like that of a fish's tail : it is all under water except 

 the crank, and part of the connecting rod. 



Improved Screiv-Propelling Engines. Mr. Salter, of London, has introduced 

 a new arrangement of steam-engine, particularly adapted for screw-propeller 

 navigation. It may be considered a semi-rotary, reciprocating engine, having 

 two curved cylinders, the pistons of wihich, at every stroke, travel over a seg- 

 ment of a circle ; and the piston-rods being connected by toggle-joints to the 

 crank on the screw-propeller shaft, each revolution is effected with a minimum 

 amount of friction. The valves are so arranged that the induction port opens 

 very small, allowing the injection only of a puff of steam, while at the end 

 of the stroke the exhaust-valve opens to the fullest extent, giving instantan- 

 eous Jreedom to the return-stroke of the piston. 



Side Screw Steamers. The steamer Baltic, of Lake Erie, once a paddle- 

 wheel boat, was divested of her paddles and engines last year, and has been 



