MECHANICS AND USEFUL ARTS. 47 



rator. The respirator consists of a number of layers of wire-gauze, or metal 

 plates, which become highly heated at one end from their proximity to the fire. 

 High-pressure steam being admitted into the regenerator, passes through the 

 respirator into the working cylinder. Arriving there in a highly-heated and 

 compressed state it raises the piston. Becoming cool by expansion, it again 

 passes into the regenerator, at the temperature of saturated steam and of 

 atmospheric pressure. Being pressed back into the working cylinder after the 

 piston has recovered its return stroke, it is mixed with a small additional 

 amount of steam from the boiler. It thus recovers its tension, and again 

 expands and becomes heated in the working cylinder. Although high tem- 

 perature is resorted to in this engine, all its working parts are of the ordinary 

 temperature of saturated steam. Mr. Siemens stated that this engine would 

 consume much less fuel than TTatt's, and that several engines had been 

 erected in France, Germany, and England, which had hitherto worked very 

 satisfactorily. 



RECENT IMPROVEMENTS IN STEAM ENGINES. 



Stevens 1 Improved Steam Boilers. A patent has been recently granted to 

 J. Lee Stevens, a well known English inventor, for an improved combina- 

 tion of the parts of a boiler by which air is to be more advantageously 

 applied and combined with the products of combustion ; the boiler is formed 

 with a water space above the furnace, and above this space there is a return 

 flue through which the products of combustion pass to a chamber called " the 

 igniting box." From this chamber the tubular flue passes to a chamber flue 

 at the opposite end of the boiler. In front of the " igniting chamber" there 

 is a double cover pierced with holes through which streams of air pass, to 

 mix with the products of combustion before they pass through the tubular 

 flues. 



New Method of Stopping Steam Engines. Mr. Dugdale of Paris, France, 

 has invented some improvements in the construction of locomotive engines, 

 applicable in part to marine and stationary engines, which relate to a novel 

 mode of stopping or retarding the progress of locomotive steam engines. In 

 effecting this object, the steam is converted from a propelling to a resisting 

 medium, and thereby suddenly presents an elastic obstruction to the advan- 

 cing piston in the steam cylinder. Over the steam ports of the working 

 cylinder a slide valve is applied, composed of iron and steel plates attached 

 together, the steel face being to receive the ordinary brass cut-off and supply 

 valve, and the iron face lying close to the planed face of the steam ports. 

 This intermediate valve is so arranged, that when the break is required to be 

 put into action, it shall slide on its seat, and intercept the passage of the 

 steam to the exhausted side of the piston, and permit the steam to be sup- 

 plied to the opposite side. A cushion of steam will thus be opposed to the 

 advancing piston, and if displaced by the impetus of the engine acting on the 

 piston, a similar obstruction will then be offered to the other side of the piston 

 as it advances, and so on until the action of the engine is suspended. This 

 composite valve the inventor proposes to apply to steam engines generally, 



