Iron filings or borings, when mixed with sulphur, sal ammoniac, etc, expand and form a compact mass which makes a very firm steam-tight joint if properly applied. Concerning this cement, Dr. Ure says: The iron rust cement is made of 50 to 100 parts of iron borings, pounded and sifted, mixed with 1 part of sal ammoniac, and when it is to be applied, moistened with as much water as will give it a pasty consistence. Formerly, flowers of sulphur were used, and much more sal ammoniac in making this cement, but with decided disadvantage, as the union is effected by oxidation, and the consequent expansion and solidification of the iron powder, and any heterogeneous matter obstructs the effect The best proportion of sal ammoniac is 1 per cent, of the iron borings. (2) Mix 4 parts of fine borings or filings of iron, 2 of potter's clay, and 1 of powdered firebrick, and make them into a paste with salt and water. When this cement is allowed to concrete slowly on iron joints, it becomes very hard. (3) Coarsely powdered iron borings, 5 lb.; powdered sal ammoniac, 2 oz.; sulphur, 1 oz.; and water sufficient to moisten it. This composition hardens rapidly; but if time can be allowed, it sets more firmly without the sulphur.

It must be used as soon as mixed, and rammed tightly into the joints. (4) Sal ammoniac, 2 oz.; sublimed sulphur, 1 oz.; cast-iron filings or fine turnings, 1 lb. Mix in a mortar and keep the powder.dry. When it is to be used, mix it with 20 times its weight of clean iron turnings or filings, and grind the whole in a mortar; then wet it with water until it becomes of convenient consistence, when it is to be applied to the joint. After a time it becomes as hard and strong as any part of the metal. (5) The following is said to form a very hard cement: Take a few spoonfuls of iron filings, and oxide of iron in the form of black scales which fall from red-hot bars of iron in blacksmiths' shops: crush them fine with a hammer, mingle with the powder an equal bulk of the best Portland cement, and render the mass plastic by adding the white of eggs, and work for a few minutes, until the plastic material is about of the consistence of soft putty. Only a small quantity should be prepared at once, as it will set in a short time. (6) A correspondent of the English Mechanic says that he has used the following recipe with the greatest success for the cementing of iron railing tops, iron gratings to stoves, etc, and with such effect as to resist the blows of the sledge hammer: - Take equal parts of sulphur and white lead, with about a sixth of borax, incorporate them so as to form one homogeneous mass.

When going to apply it, wet it with strong sulphuric acid, and place a thin layer of it between the two pieces of iron, which should then be pressed together. In 5 days it will be perfectly dry, all traces of the cement having vanished, and the iron will have the appearance of having been welded together. (7) 5 parts sulphur, 2 of graphite, and 2 of fine iron filings are melted together, taking care that the sulphur does not catch fire. The parts, previously warmed, are covered with the cement, reduced to a pasty consistence on a fire, and firmly pressed together. This cement, it is said, is very well adapted to fill out leaks in cast-iron vessels. (8) For Hot-Air Pipes. 60 parts (by measure) of chalk, 20 of limestone or lime, 20 of salt, 10 of brawsey sand, 5 iron filings, and 5 of red or blue clay, properly mixed together, triturated, and calcined. (9) For Hot-Water Cistern. To 4 or 5 parts clay dried and pulverized, add 2 of fine iron filings free from oxide, 1 of peroxide of manganese, 1/2 of sea-salt, and 1/2 of borax. Thoroughly incorporate these in .as fine a state as possible, reduce them to a thick paste with water, and use immediately. It should then be exposed to a heat, gradually increasing to almost a white heat.

This cement resists heat and boiling water. (10) Glycerine and litharge, stirred to a paste, harden rapidly, and make a tolerable cement for iron upon iron, for two stone surfaces, and especially for fastening iron in stone. This cement is insoluble, and is not acted upon by strong acids. (11) You can cement cloth to polished iron shafts by first giving them a coat of best white-lead paint; this being dried hard, coat with best Russian glue, dissolved in water containing a little vinegar or acetic acid. (12) For Iron and Glass. Copal varnish 15 parts, drying oil 5, turpentine 3, oil of turpentine 2, liquefied glue 5; to be all melted in a water-bath, and add 10 parts of slaked lime. (13) For cast-iron cisterns of large dimensions: composed of sal ammoniac, clean borings, and urine, mixed one day before required. The proportions are 1 lb. sal ammoniac to 100 lb. borings, with sufficient urine to make a stiff paste - to be well driven into the joints with a caulking tool a little narrower than the space between the flanges. Give at least 3 days to set before filling cistern with water. The cement sets us hard as the metal itself. (14) Iron borings, 12 lb.; sal ammoniac, 2 oz.; sulphur 1 oz.; water q.s. (15) Iron borings 7 to 8 lb., sal ammoniac, 2 oz., water as before.

The strongest lute, perhaps, is (15); but when the work is required to dry rapidly, as in the case of steam joints wanted in a hurry, the quantity of sal ammoniac must be slightly increased, and a very little sulphur must be added. This addition causes quicker setting, but reduces the strength. The power of these lutes is dependent upon the oxidation and consequent expansion of the mass, therefore the less foreign matters they contain, the better. They should be made up only as they are required, as they spoil rapidly; when containing much sulphur, they may become quite hot in a few hours, and combustion has been known to take place in them when left together in quantity for a night.

(16) Finely sifted iron filings, 60 parts; finely powdered sal ammoniac, 2 parts; flowers of sulphur, 1 part. This powder is made into a paste with water, and immediately applied; it soon sets as hard as the iron it is intended to lute.

(17) For iron pots and pans. 2 parts sulphur, 1 of graphite; the sulphur is held in an old iron pan over the fire till it begins to melt; the graphite is then added, and the mass well stirred till thoroughly melted and combined; then poured out on an iron plate or smooth stone, and broken up when cold. Used like solder with a soldering iron. Holes should first be filled with a rivet, and then cemented over.