Wear of Iron and Steel Rails.
mate determination of the variations in magnetic intensity. This method seems applicable, on ship-board, for the correction of the compass, especially when the indications of the needle may be deceptive, on account of the neighborhood of magnetic rocks, or of islands rich in iron ores. The inventor also suggests the use of a bar of soft iron, several metres in length, having, at one end, a magnetic coil with a self-registering apparatus. The pitching of the vessel would excite induction currents, and the diagram on the register would reveal the direction of the vessel, so as to check the indications of the eompass.--Uomptes l~endus. C. C o m p a r a t i v e W e a r of I r o n a n d S t e e l R a i l s . - - N e a r Oberthausen, on the line from Cologne to Minden, a variety of rails were laid in 1864, and taken up in 1876. The traffic was very great, and the percentage of replacement in twelve years was as follows: Wrought iron rails, from the Frederich-Wilhelm works, 80"66; wrought iron, from Ph~nix works, 6800; puddled steel, of Funke & Co., 33"33; puddled steel, of Hosch & Sons, 33'38; Hosch & Sons' Bessemer, 4'70; Krupp's Bessemer, 4"08; HSrder-Verein Bessemer, 1"33.--Annales lndustr. C.
Composition of Ancient Glass.--religot has lately been engaged upon various analyses of glass, and turned his attention especially towards some of the oldest specimens that he could find. There is considerable difference in the composition of modern glass in different districts, but all manufacturers agree in employing three materials, lime and silex being almost invariably used, with either potash or soda as a flux. The glass-makers of antiquity used only sand and an alkali, and this is one reason why their glass had so little durability. The credit of inventing flint glass, Or the modern crystal, is due entirely to the English.mAnn. de. Chem. et de Phys. C. Harmonic Strim.--C. Deeharme has studied the relation which exists between the breadth of the strim, which are produced in a thin layer of water upon a vibrating circular plate, and the number of corresponding sound-vibrations. Photographing the net-work of nodes and internodes, and measuring the stri~e, he finds that their breadths are inversely proportional to the square-roots of the numbers of vibrations in the corresponding sounds.--Comptes Rendus. C.