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To Protect Iron from Rust

left in the end of the trough, to allow of a bar A mastic or covering for this purpose, propos- being drawn out for examination. When a ed by M. Zeni, is as follows: Mix 80 parts bar, on being withdrawn and broken, has acpounded brick, passed through a silk sieve, quired a crystalline texture, the metal is alwith 20 parts litharge; the whole is then lowed to cool down gradually, some days rubbed up by the muller with linseed oil, so being allowed for this, and the charge, when as to form a thick paint, which may be diluted cool, withdrawn from the trough. The bars with spirits of turpentine. Before it is applied the iron should be well cleaned. From an experience of 2 years upon locks exposed to the air, and watered daily with salt water, after being covered with 2 coats of this mastic, the good effects of it have been thoroughly proved. will be found covered with large blisters, hence the name of the process, and increased about To in weight. The steel is now sufficiently good for files and coarser tools, but for finer instruments, several varieties of finer steel are required. (Makins).

3275. Το Make Shear-Steel. This is 3270. To Prevent the Decay of Iron produced by cutting up bars of blistered steel, Railings. Every one must have noticed the into lengths of 30 inches, and binding them destructive combination of lead and iron, in bundles of 8 or 9 by a ring of steel, a rod from railings being fixed in stone with the being fixed for a handle. These are brought former metal. The reason for this is, that to a welding heat, and welded together under the oxygen of the atmosphere keeps up a a tilt hammer. The binding ring is then regalvanic action between the two metals. moved; and, after reheating, the mass is This waste may be prevented by substituting forged solid, and extended into a bar. In zinc for lead, in which case the galvanic influ- cases where this operation is repeated, the ence would be inverted; the whole of its steel is called double-shear steel. (Makins.) action would fall on the zinc; the one remain- 3276. To Make Cast-Steel. Cast-steel ing uninjured, the other nearly so. Paint is the best variety for all fine cutting tools. formed of the oxide of zinc, for the same This is a mixture of scraps of different vareason preserves iron exposed to reason preserves iron exposed to the atmo- rieties of blistered steel, collected together in a ordinary paint good refractory clay crucible; upon this a composed of the oxide of lead.

3271. To Scour Cast Iron, Zinc, or Brass. Cast iron, zinc, and brass surfaces can be scoured with great economy of labor, time and material, by using either glycerine, stearine, naphthaline, or creosote, mixed with dilute sulphuric acid. cover is luted, and it is exposed to an intense heat in a blast furnace for 3 or 4 hours. The contents are then run into moulds. After being subjected to the blows of a tilt-hammer, the cast steel is ready for use. (Makins).