L. MECHANICS AND ENGINEERING. 513 



the material in the shape of thin sheets to be cut as required ; 

 and in this case the mass is rolled out upon a slightly heated 

 plate. Mr. Pichler asserts that this composition hardens 

 rapidly, and can be easily polished. When kept for a length 

 of time, it should be Avrapped in a moist sheet, and exposed 

 to jxentle heat before using^. The variesfated marble -like 

 veins can also be produced by kneading together differently 

 colored portions of this mass. 8 6', 1872, xxx., 237. 



PEODUCTION or IRON EAIL IN THE UNITED STATES IN 1872. 



The Bulletin of the American Iron and Steel Association 

 publishes the following statistical account of the iron- rail 

 production of the United States for the year 1872, the total 

 yield footing up a considerable increase upon the figures of 

 the preceding year. The aggregate (reported) manufacture 

 amounted to 941,992 net tons, as compared with 775,733 

 tons produced in 1871. These figures include only rails 

 made for freight and passenger railways, and exclude some 

 15,000 tons of street rails and mining rails, which as a rule 

 are classified as bar-iron. The chief production is divided 

 between Pennsylvania, Ohio, and Illinois Pennsylvania, as 

 usual, leading the list with 419,529 tons, or forty-four and a 

 lialf per cent, of the whole. 



SURFACE HARDENING OF CAST IRON. 



The wearing of cast-iron surfaces exposed to sliding fric- 

 tion can be almost wholly prevented by tempering the sur- 

 face with a mixture of 21y\j- pints of water, 30f pounds of 

 sulphuric acid, and 1003 grains of nitric acid. The article 

 should be heated to a cherry-red, and protected from the 

 oxidizing effect of currents of air by a sheet-iron box. The 

 process is especially adapted to the hardening of bearings of 

 axles, which, while much cheaper than those of the usual 

 alloy, will, when regularly lubricated, last as long, even when 

 there is great rapidity of motion. 5 (7, 1872, li., 408. 



IMPROVEMENT IN PUDDLING IRON. 



According to the Journal of the Franklin Institute^ a suc- 

 cessful experiment has been made in Germany in the direc- 

 tion of improving the qualities of pig-iron, by puddling in 

 contact with a small percentage of fluor-spar. The object of 



Y2 



