MECHANICS A3TD USEFUL ARTS. 47 



order to enable the trains to turn into the sharp valley, it will be 

 necessary to have the entrance in a curve. The curved part of the 

 tunnel is now being commenced, and will join the straight part at 

 about 250 yards from its present temporary entrance on the Italian 

 side. 



The tunnel will have a continuous gradient, falling from the Savoy 

 end towards Italy, at the rate of 1 in 500. It is to be regretted that 

 the approaches are so steep, being on an average 1 in 50 on one side, 

 and 1 in 40 on the other. It would have been far better to have 

 made the tunnel somewhat longer, so as to have avoided a continual 

 source of wear and tear, both of trains and rails, which will be a per- 

 petual charge upon the line. The height of the tunnel at its Italian 

 entrance above the level of the sea is 4,331 feet. 



NEW RUDDER. 



A new rudder, the patented plan of Mr. Lumley, has recently been 

 put on trial by the English admiralty. Its peculiarity consists in its 

 being cut in two vertically, and the two parts being connected 

 together by gudgeons and pintles in a manner precisely similar to 

 the ordinary method of hanging a rudder to a ship's sternpost. At 

 the outer part of the rudder's afterpiece are attached two chains 

 which pass through the main piece of the rudderj one on each side. 

 The result of this arrangement is that on the rudder's being moved 

 over either to starboard or port the chain becomes taut and brings 

 the outer piece of the rudder over at a sharper angle than the main 

 piece, and thus presents a hollow surface to, and obtains a greater 

 hold on, the water than can be obtained with the ordinary rudder, 

 and without bringing any very great strain to bear upon the gud- 

 geons and pintles. 



ELECTRIC TELEGRAPH AND GAS ON SHIPBOARD. 



One of the new iron-plated frigates recently launched in Great 

 Britain the Resistance has two specialities of equipment which 

 are seldom found on board ship, the electric telegraph and gas. 

 The former forms a communication between the fore and after 

 bridges, and by the officer of the watch, at sea, moving a handle on 

 a dial-plate, a needle in a case hanging in front of the quarter-master 

 at the wheel points to the signal wished to be given, starboard, port, 

 or steady, as required. The whole arrangement is very simple, and 

 cannot well be misunderstood, either by the officer working the han- 

 dle on the forward bridge, or the man at the wheel. The gas is man- 

 ufactured from oil. The gasometer is on the upper deck, between 

 the boom boats and before the main hatchway, in a small caboose. 

 The oil, flowing from a reservoir through a small pipe, enters a retort, 

 whence the gas generated by the heat passes into the gasometer. 

 From the gasometer a pipe conveys the gas below to the engine- 

 room and screw alley, which last is lighted by twelve burners. 



DOUBLE SCREW STEAMSHIP. 



The experiment of fitting a vessel with two screws and engines, 

 working separately and independently of each other, has recently 



