MECHANICS AND USEFUL ARTS. 99 



of manganese, manufactured from a manganesian red hematite, the 

 metal was hard, white, and granular-crystalline, with few intersecting 

 plates of crystals. The specific gravity was 7.330. These alloys of 

 manganese and iron are not generally understood by iron masters, 

 founders, and refiners, and are frequently mistaken for iron containing 

 sulphur or phosphorus. Manganesian iron is unfit for foundery purpo- 

 ses, but makes the best kinds of malleable wrought-iron when refined 

 in the forge or puddling-furnace. It " comes to nature " slowly, and 

 hence makes a good mixture with iron rich in carbon, which " comes 

 to nature too quickly," and is liable, therefore to be badly refined, 

 breaking up under the tilt-hammer, or " brooming up " in the process 

 of hammering. It is obvious that there is a loss in weight in iron in 

 purchasing the highly manganesian irons, but in those containing but 

 little manganese it is of no account, since it merely displaces a certain 

 proportion of carbon. It appears from the relative specific gravity of 

 the samples analyzed, that a highly manganesian iron may be readily 

 known, its specific gravity being less than that of ordinary white car- 

 boniferous iron. 



MALLEABLE BRASS. 







M. ELSNER, in a Prussian periodical, says it is well known that 

 common brass, containing from 27.4 to 31.8 per cent, of zinc, and 

 from 71.9 to 65.8 per cent, of copper, is not malleable while hot, but it 

 is of great importance to have an alloy of this kind which is malleable. 

 M. Machts has found that, by melting together thirty-three parts of 

 copper and twenty-five parts of zinc, there is a loss of three parts, thus 

 making sixty per cent, of zinc and forty per cent, of copper. The 

 color of this alloy is between that of brass and tombac ; it has a strong 

 metallic lustre, a fine close-grained fracture, and great solidity. Its 

 hardness is the same as that of fiuor spar ; it is consequently harder 

 than copper, is very tough, and in a properly managed fire is mallea- 

 ble, so much so that a key was formed out of a cast rod. In melting 

 the metals together, care must be taken not to permit too great a loss 

 of zinc. London Mining Journal, Nov. 9. 



ACCURATE AND SUCCESSFUL ENGINEERING. 



A HIGHLY successful and curious feat in engineering was accom- 

 plished in the month of September, at Seaford, England, in the blow- 

 ing down, by one blast of gunpowder, an immense section of chalk 

 cliff, the amount of which has been estimated at nearly 300,000 tons. 

 The object in view was to obtain materials for the protection of a beach 

 against the encroachments of the sea. The cliffs from which it was 

 determined to obtain these materials are composed of chalk, and vary 

 in height from two to three hundred feet. At a point about fifty feet 

 above high-water-mark, there was excavated a tunnel or gallery sev- 

 enty feet long, six feet high, five feet broad, ascending with a slope of 

 one foot in three feet. At the inland extremity it turned right and left 

 in the heart of the cliff, above fifty feet one way and above sixty the 



