TRANSACTIONS OF THE SECTIONS. ll'J 



The employment of muddy and salt water for condensation of steam and for 

 maintaining a vacuum in marine engines is well known to be disadvantageous, so 

 much of the power of the engine being employed in the process of exhaustion by 

 the air-pump. 



The application of the screw-propeller for a ship at sea has called attention to the 

 means most simple and effective for obtaining for such propellers a rapid motion, 

 whereby to ensure high speed for the ship. 



These are among the considerations which have led to the discovery that the steam, 

 after it has exerted its power on the piston, may be condensed instantly by being 

 conducted into a receiver or receivers placed longitudinally vj^ithin a vessel, and on 

 each side, filled after the manner of tubular boilers, with metallic tubes inserted into 

 metallic plates of ample substance to ensure perfect tightness, and each end of which 

 is connected with the water of the sea or river by a bent tube and apertures made 

 in the sides of a ship or vessel. 



This method has been for several years adopted to great advantage. 



" It was mentioned by myself to the Mechanics' Section of the British Association 

 for the Advancement of Science two years since, when their Annual Meeting was held 

 at Swansea, but it was named only incidentally in "the course of some discussion on 

 marine engines, and I am not aware that it has ever claimed the attention which 

 further experience has shown it merits. I therefore avail myself of the occasion which 

 is now presented to me to place before the view of the meeting facts fairly proved 

 by the Neath Abbey Iron Company as makers, and myself as associated with them, 

 and as an owner of several of these marine engines ; that even high steam may be 

 safely employed in such vessels in what, for facility of description, I will call loco- 

 motive boilers ; that such steam gives a rapid motion to the piston, and that this 

 action may be conveyed direct to the crank, giving motion to a shaft and propeller 

 without any multiplying wheel ; that the steam so employed may be condensed by 

 being at once conveyed from the cylinder into the receiver within the vessel, furnished 

 with metallic tubes, through Xvhicli the water of a river or the sea shall rapidly pass ; 

 that such water so passing through the tubes of a receiver maintains coldness to a 

 great extent in the interior of such receiver ; that the steam passing from the cylinder 

 into such receiver becomes instantly, condensed, though still retaining heat enough 

 for advantageously feeding the boiler with fresh water ; that by these means little 

 or no vacuum can be obtained independently of the power of the engine employed in 

 other vessels in working the air-pump ; that the water so condensed is again, by 

 pumping, transferred to the boiler, and that thus the supply of fresh water taken in 

 at starting serves, as far as I have proved it, for a voyage from port to port for one 

 day ; that hereby the boiler is kept free from salt or mud, and does not require to 

 be blown out to clear it from salt, and thus time and power are further oeconomized ; 

 and that under all these circumstances a higher speed may be acquired for a vessel 

 with the same size cylinder and boiler, and an ceconomy of fuel to a considerable 

 extent is the result. 



" I have a steamer, called the Princess Royal, on this principle in daily use in the 

 Bristol channel, where the advantages of this method of condensing are obvious. 

 The fuel consumed is not more than two-thirds of that used in a timber vessel with 

 engines of equal power on the old plan, running the same distance ; the speed of 

 this iron vessel is greater by one-third, and its power to carry cargo nearly doubled. 



" I have also two small passenger-boats on the Bristol dock basin, plying from Bris- 

 tol to the Hot Wells, the Expert and Express, the engines of which are on the same 

 condensing principle. Large condensers may exert a partial vacuum. The respec- 

 tive forms of the two vessels proves this result." 



On Mechanism to explain the Pendulum Experiment. 

 By Richard Roberts, C.E. 



The first model, by reference to which Mr. Roberts explained his view of the sub- 

 ject, consisted of a railway upon a board, mounted on three balls, as feet, and upon 

 that board a smaller board was mounted on four wheels like a railway waggon ; upon 

 the waggon a swan-necked piece of iron was secured, the upper end of which was 

 bored to receive an axle representing a prolongation of the imaginary ajcis of the earth. 



