46 ANNUAL OF SCIENTIFIC DISCOVERY. 



chest the mixture passes to the cylinder of the engine, and actuates the 

 piston in the usual manner. 



The results attained to by Mr. Isherwood, in a series of experiments, 

 were briefly as follows : 



Using the steam simply surcharged, produced, with the same fuel, an 

 increased effect of sixty-five per cent, over what was obtained with the 

 saturated, or ordinary steam alone ; while an increased effect of one hun- 

 dred and six per cent, was produced by the use of the mixture. Also, the 

 increased effect of the mixture was twenty-five per cent, over what was 

 obtained from the surcharged steam alone. 



NEW PLAN FOR USING STEAM EXPANSIVELY. 



Mr. B. F. Day has presented to the Franklin Institute, a plan of an 

 engine for using steam expansively in a second cylinder. The difference 

 between this engine and others operating on the same principle that have 

 preceded it, is in contradistinction from allowing the steam to pass directly 

 from one cylinder to another ; the taking of the steam from the receiving 

 cylinder to steam-chests provided with valves and posts, by and through 

 which the steam is admitted to, and exhausted from, the second cylinder, 

 by which means it is claimed, that a longer expansive action of the steam 

 is retained. Another difference consists in surrounding the second cylin- 

 der, when used in connection with a receiving cylinder, with a flue, through 

 which the unconsuined combustible gases are passed after leaving the 

 furnace, by which any loss from radiation will be avoided, and the steam 

 in the cylinders will, to some extent, be reached by caloric. 



ON BOILER EXPLOSIONS. 



r 



At the British Association, a communication on boiler explosions gave 

 rise to a discussion on the causes of such explosions, and on the effect of 

 percussion in weakening the strength of iron, in which Mr. Fairbairn, 

 Mr. Roberts, Mr. Hopkinson, Mr. Oldham, and other members took part. 

 Mr. Fairbairn said, that, so far as his experience went, the explosions of 

 boilers generally occur at the moment the engines start, in consequence 

 of the sudden generation of steam by the increased motion given to the 

 water. With respect to the weakening of railway axles by use, he con- 

 ceived that effect to be produced rather by the continuous bindings of the 

 metal, however small they may be, which give a set to the fibres and 

 increase the liability to break. Boiler-plates are also frequently injured 

 by the operation of punching for melting. Mr. Roberts attributed boiler 

 explosions in most instances to the defective construction. He was of 

 opinion that in riveting boiler-plates the rivets are seldom made large 

 enough, large rivets being much stronger than small ones. Mr. Clay said 

 the crystalline structure of wrought iron acqxiired by long continued per- 

 cussion might be restored to the fibrous state by reheating. Mr. Oldham 



