MECHANICS AND USEFUL ARTS. 27 



tlie l^oiler below the lowest level of the water, the other above the 

 highest, so that steam only shall pass throus^h the latter. 



"When the engines have external C3'linders, the exhaust-pipe 

 divides into two branches. The injection-tube must therefore 

 have also two branches ; one going to the under side of each 

 branch of the exhaust-pipe. The bifurcation should be perfectly 

 symmetrical, so that the water held in suspension in the steam 

 may not take the line of steepest descent, and that the distribution 

 to each cylinder may be equal." 



CAR-WHEELS. 



From Auchincloss' Report of the Paris Exhibition we extract 

 the following: — 



" The practice of nations seems much divided on the subject 

 of the proper material for car-wheels. The wrought-iron wheel 

 is almost exclusively adhered to in England, France, and Prussia ; 

 while Holland and Austria discover features worthy of attention 

 in the cast iron. The general properties of the cast-iron spoke 

 wheel are familiar to all. The society of Providence (limited), 

 whose office is at 208 Quai Jemmapes, Paris, display specimens 

 of rolled wrought-iron wheel centres, without weld, whose radial 

 section is similar to an I-beam. Upon such centres the tire is 

 held with 4 seven-eighth inch rivets. 



" The Society of Mines and Steel Works, Bochum, Prussia, 

 exhibits a remarkable cast of wheels. It was formed by 

 stacking the flasks 22 wheels high, with the hubs in contact, 

 and then pouring in crucible steel through a side-runner. Al- 

 though this cast was made more as a matter of curiosity, it is 

 quite customary with this company to arrange them in tiers of 

 6 wheels each, and thus save the numerous side-runners re- 

 quired when cast singly. One swinging of the set in the lathe 

 answers for facing up all the treads and flanges. These wheels 

 have a single plate, and are 40 inches in diameter. The Aus- 

 trian exhibitions are by A. Ganz, of Ofen, Hungary, and Mr. 

 Derno, of the same section of country. The former gentleman 

 is the most extensive manufacturer in Austria, and makes a 

 double-plated wheel, similar in design to that known in America 

 as the ' Snow Patent.' He exhibited a wheel 38 inches in diame- 

 ter, cast in 1856, which has served under a 10 ton four-wheeled 

 wagon for the past 11 years. The tread of this wheel appears 

 in excellent condition, the metal close-grained without signs of 

 honey-combing. 



"The director-general of the Austrian I. R. P. State Railway 

 Society certilies to the fact of this wheel having run 50,000 miles. 

 The road on which these wheels are used is 419 miles in length, 

 and pursues a south-easterly course from Vienna through Hunga- 

 r3\ In respect to climate the trial is most severe. Its merits are 

 certainly appreciated or the shop number would not extend as 

 high as 84,981, which was noticed on a wheel cast during the 

 picsent year. The wheels, as usual, have 3 core-holes in the 

 back. The only peculiarity about these holes is a V-groove cast 



