L. MECHANICS AND ENGINEERING. 521 



boiler surface. The addition of one pound of glycerine to 

 every three or four hundred pounds of coal burned is said to 

 answer all necessary requirements. 1 Z>, 3farch, 1873, 157. 



VALUE OF THE STEAM-JACKET FOR ENGINES. 



An animated discussion has lately taken place, before the 

 Scientific and Mechanical Society of Manchester, as to the 

 value of the steam-jacket around the cylinder of a steam-en- 

 gine in aiding in the working of the engine by preventing 

 the too rapid loss of heat. Mr. Hildebrand mentions, as 

 among its advantages, that it slightly increases the power 

 of the engine, and insures greater immunity from break- 

 downs caused by an accumulation of water in the cylinder; 

 but that, on the other hand, it entails a positive waste of fuel, 

 greater labor in attendance, and an increased outlay of capi- 

 tal to the amount of twenty per cent. For these reasons he 

 concludes that the question as to economy must be answer- 

 ed in the negative. The case of hot-air jackets will form an 

 exception, provided the hot air or other hot gas would other- 

 wise be wasted. But here come in the objections that the 

 extent of superheating is not under as good control as with 

 steam, and if carried too far impairs the durability of the cyl- 

 inder, by depriving it of a moderate moisture necessary as a 

 lubricant for the piston. 3 A, 3Iarch 15, 1873, 262. 



wendt's toesion cak-spring. 



Wendt, the chief locomotive engineer of the Berlin and 

 Gorlitz Railroad, has obtained a patent for a car-spring which 

 depends upon torsion instead of flexion, as in the ordiriary 

 plate springs, and which, it is claimed, is less liable to break, 

 gives greater security, with twenty per cent, heavier load, is 

 cheaper, and is easily attached to the car. Incomplete ex- 

 periments on the above road indicate that the running is 

 without danger, even after the accidental breaking of one 

 spring. 13 C, Se2)tember 15, 1872^ 1224. 



SCREW RAIL^VAY BRAKE. 



Mr. William Kimball, of Woburn, Mass., has recently pat- 

 ented a brake, constructed on the principle of the screw, 

 whose connections, it is claimed, can only with difiiculty be 

 put out of order or broken, Avhose motions are Avith^ut loss 



