CEMENTS.

Shell-lac Cement, or Liquid Glue. -Fine orange shell-lac, bruised, 4 oz.; highly rectified spirit, 3 oz Digest in a warm place, frequently shaking, till the shell-lac is dissolved. Rectified wood naphtha may be substituted for spirit of wine, where the smell is not objectionable. This is a most useful cement for joining almost any material.

Shell-loc Cement, without Spirit.—Boil 1 oz of borax in 16 oz. water; add 2 oz. powdered shell-lac, and boil in a covered vessel till the lac is dissolved This is cheaper than the above, and for many purposes, answers very well. Both are useful in fixing paper labels to tin, and to glass when exposed to damp.

Keller's Armenian Cement, for Glass, China, &c.-Soak 2 dr. of ent isinglass in 2 oz of water for 24 hours; boil to 1 oz; add 1 oz of spirit of wine, and strain through linen. Mix this, while hot, with a solution of 1 dr. of mastic in 1 oz of rectified spirit, and triturate with dr. powdered gum ammoniac, till perfectly homogeneous

Dr. Ure's Diamond Cement.-Isinglass, I oz; distilled water, 6 oz.; boil to 3 oz, and add 14 oz. of rectified spirit. Boil for a minute or two, strain, and add, while hot, first, I oz of a milky emulsion of ammoniac, and then 5 dr. of tincture of mastic.

Haenle's Cement, for Glass or Earthenware-Shell-lac, 2 parts; Venice turpentine, 1 part Fuse together, and form into sticks.

Cheese Cament, for Earthenware, &e-Mix together white of egg, beaten to a froth, quick-lime, and grated cheese. Beat them to a paste, which forms an excellent cement.

Chord Consent.Add † pint of vinegar to ‡ pint of skimmed milk. Mix the curd with the whites of 5 eggs well beaten, and sufficient powdered quick-lime to form a paste. It resists water, and a moderate degree of heat.

Cement for joining Spar and Marble Ornaments, &c.—Melt toge ther & parts of resin, 1 of wax, and stir in 4 parts, or as much as may be required, of Paris plaster. The pieces to be made hot.

Hemsler's Cement--Grind 3 parts of litharge, 2 of recently burnt lime, and of white bole, with linseed oil varnish. This is a very tenacious cernent, but it takes considerable time to dry.

Singer's Coment, for Electrical Machines and Galvanic Troughs. Melt together 5 lbs. of resin, and 1 lb. of beeswax, and stir in 1 lb of red ochre (highly dried, and still warm), and 4 oz of Paris plaster, continuing the heat a little above 212°, and stirring constantly till all frothing ceases. Or (for troughs), resin, 6 lbs; dried red ochre, 1 lbs; calcined plaster of Paris, lb. ; linseed oil, ↑ Ib.

Composition for welding Cast Steel-Take of borax, 10 parts, sal ammoniac, 1 part; grind or pound them roughly together then fuse them in a metal pot over a clear fire, taking care to continue the heat until all spume has disappeared from the surface. When the liquid appears clear, the composition is ready to be poured out to cool and concrete; afterwards, being ground to a fine powder, it is ready for use. * * To use this composition The steel to be welded is first raised to a "bright yellow" heat, it is then dipped among the welding powder, and again placed in the fire, until it attains the same degree of heat as before; it is then ready! to be placed under the hammer.

Cast-Iron Cement.-Take of clean iron borings, or turnings, 1 cwt.; of sal-ammoniac 8 oz ; and 1 oz. of flour of sulphur. Mix them thoroughly, and add sufficient water. If the cement is not to be immediately used, care should be taken to keep the mixture soaked in water; if left dry, the cement will heat, and be spoiled.

Cement for Steam Pipe Joints, &c., with Faced Flanges-To 2 parts of white lead mixed, add 1 part of red lead dry, grind, or otherwise mix them, to a consistence of thin putty, apply interposed layers, with one or two thicknesses of canvas or gauze wire, as the necessity of the case may require.

Glues-1. A very strong glue is formed by throwing a small quantity of powdered chalk into melted common glue.

2. To make a glue which will resist the action of water-boil one pound of common glue in two quarts of skimmed milk.

Botany Bay Cement.-Take 1 part of Botany Bay gum, and melt and mix it with 1 part of brickdust.

Cap Cement.-As Singer's; but 1 pound of dried Venetian red may be substituted for the red ochre and Paris plaster.

Bottle Cement-Resin 15 parts; tallow 4 (or wax 3) parts; highly dried red ochre 5 parts. The common kinds of sealing-wax are also used.

Turner's Cement -Beeswax 1 oz.; resin oz.; pitch oz. Melt, and stir in fine brickdust.

Coppersmith's Cement.-Powdered quick-lime, mixed with bullock's blood, and applied immediately.

Engineers' Cement.-Fqual weights of red and white lead, with drving oil, spread on tow or canvas. This is an admirable composition for uniting large stones in cisterns, &c.

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Iron Cement for Closing the Joints of Iron Pipes.—Take of iron borings, coarsely powdered. 5 lbs. of powdered sal-ammoniac 2 oz.; of 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.

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Cement for Steam Pipes.-Good linseed oil varnish ground, with equal weights of white lead, oxide of manganese, and pipeclay.

Gad's Hydraulic Cement.-Powdered clay 3 lbs. ; oxide of iron 1 lb; and boiled oil to form a stiff paste.

Cements for Masonry of Chambers of Chlorine, &c.-Equal parts of pitch, rosin, and plaster of Paris.

Roman Cement.-1 bushel of slacked lime; 3 lbs. of green copperas; and bushel of fine gravel sand. The copperas should be dissolved in hot water. It must be stirred with a stick, and kept stirred continually while in use. Care should be taken to mix at once as much as may be requisite for one entire front, as it is very difficult to obtain the same shade or color a second time. It ought to be mixed the same day it is used. This is the English Roman

cement.

The genuine Roman cement consists of the pulvis puteolanus, or puzzolene, a ferruginous clay from Puteoli, calcined by the fires of Vesuvius, lime, and sand, mixed with soft water. The only preparation which the puzzolene undergoes is that of pounding and sifting; but the ingrediens are occasionally mixed with bullock's blood and suet, to give the composition greater tenacity.

Seal Engravers' Cement.-Resin 1 part, brickdust part. Mix, with heat.

Marine Cement, commonly called Marine Glue.---Cut caoutchouc into small pieces, and dissolve it, by heat and agitation, in coal naphtha. Add to this solution powdered shell-lae, and heat the whole, with constant stirring, until combination takes place; then pour it, while hot, on metal plates, to form sheets. When used, it must be heated to 280° Fah., and applied with a brush

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Liquid Glue-Dissolve bruised orange shell-lac in of its weight of rectified spirit, or of rectified wood naphtha, by a gentle heat is very useful as a general cement and substitute for giue. Another kind may be made by dissolving I oz of borax in 12 oz. of soft water, adding 2 oz. of bruised shell-lac, and boiling till dissolved, stirring it constantly.

Bank Note Glue.-Dissolve 1 lb. of fine glue, or gelatine, in water; evaporate it till most of the water is expelled; add 4 lb. of brown sugar, and pour it into moulds. Some add a little lemon juice. It is also made with 2 parts of dextrine, 2 of water, and 1 of spirit.

Maissiat's Cement, as an Air-Tight Covering for Bottles, de.Melt india-rubber (to which 15 per cent. of wax or tallow may be added), and gradually add finely powdered quick-lime, till a change of odor shows that combination has taken place, and a proper consistence is obtained.

Cement for Attaching Metal Letters on Plate Glass-Copal varnish 15 parts; drying oil 5 parts; turpentine 3 parts; oil of turpentine