and causes the residue to adhere firmly to the metal. This process is repeated several times until the required depth of colour, and hardness and finish of the surface is obtained. The varnish used consists of, methylated spirit, I quart; shellac, 4 oz.; resin, 4 oz., dissolved, and coloured with one of the following mixtures: for black colour, with ivory black, or with black made of asphaltum, 1 lb.; balsam of copaiba, 1 lb.; melt and thin with hot oil of turpentine. Another black consists of: asphaltum, 3 oz.; boiled linseed oil, 1 gallon; burnt umber, 8 oz.; melt, mix, and thin with hot oil of turpentine. Another black consists of: amber, 12 oz.; asphaltum, 2 oz.; resin, 1 oz.; boiled linseed oil, pint; melt and mix, and when cooling add 1 pint oil of turpentine. Yellow colour, king's yellow White colour, white lead, ground up with a sixth of its weight of starch; thin with copal varnish,

Iron Lacquer.-Amber, 12 parts; turpentine, 12; resin, 2; asphaltum, 2; drying oil, 6. Another iron lacquer.-Asphaltum, 3 lbs.; shellac, lb.; turpentine, 1 gallon.

Black Finish for Small Articles of Iron and Steel.-Boil 1 part of sulphur in 10 parts of oil of turpentine, paint the article with it thinly, and heat over a spirit lamp until the required depth of colour is obtained.

Tinning Small Articles of Iron, Brass, or Copper by the Boiling Process. First clean well and pickle in a bath of dilute muriatic acid, and rinse well in fresh clean water; then immerse for a short time, and stir with a zinc rod, in one of the following solutions, which must be boiling hot :

Solution No. 1.-Ammonia alum, 17 oz.; soft water, 12 lbs.; protochloride of tin, 1 oz.

Solution No. 2.-Bitartrate of potassa, 14 oz.; soft water, 24 oz.; protochloride of tin, 1 oz.; and clean zinc in strips, lb.

Solution No. 3.-—Soft water, 1 gallon; grain tin, 2 lbs.; cream of tartar, 1 lbs.

Tinning Zinc.-Dip in a solution of distilled water, 1 gallon; pyrophosphate of soda, 3 oz. fused protochloride of tin, oz.

Galvanizing Iron.-Pickle the articles for 8 hours in water containing I per cent. of sulphuric acid, held in a wooden vessel; then scour well, rinse in clean water, and immerse them in a bath of melted zinc, kept covered with a layer of melted sal ammoniac to prevent oxidation of the zinc.

Black Finish for Brass.-Dissolve copper wire in nitric acid, add 3 parts of water to one of the acid, make the article hot and dip it in the solution; then heat the article over a spirit lamp until the desired depth of colour is obtained, and give one coat only of lacquer.

Black Finish for Brass.-Reduce nitrate of copper to the oxide, warm the metal slightly and apply with a brush, and then heat the article until the required depth of colour is obtained.

Black Finish for Brass.-Make a strong solution of nitrate of silver in one dish, and of nitrate of copper in another; mix the two together, and

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plunge the brass into it; remove and heat the brass evenly, until the required depth of colour is obtained.

Black Finish for Brass.-Another way is to immerse the brass until it turns black in a mixture of-white arsenic, lb. ; sulphate of iron, lb.; hydrochloric acid, 6 lbs.; when the required depth of colour is obtained, rinse well in water, dry in sawdust, polish with black lead, and lacquer. In some cases brass is simply blackened by laying on a mixture of vegetable black and french polish.

Another way to blacken brass is, first to polish it with tripoli, then wash it with a mixture of 1 part of nitrate of tin and 2 parts of chloride of gold; allow this wash to remain for nearly a quarter of an hour, and wipe off with a linen cloth.

Bronzing Brass, Copper, and other Metals.-Copper bronze:fuchsin, 10 parts; aniline purple, 5 parts; methylated spirit, 100 parts; heat, and, when solution takes place, add benzoic acid, 5 parts; next boil the whole for 10 minutes, or until the colour of the mixture changes to bronze colour.

Antique Bronze can be imitated by using the following mixture:muriate of ammonia, or sal ammoniac, oz.; salts of tartar, or carbonate of potash, drachms; vinegar, I quart. Apply with a sponge and repeat several times until the proper tint is obtained. Brown, and every shade to black use a mixture of 5 drachms nitrate of iron in 1 pint of water. Chocolate colour is obtained by steeping iron wire in aqua fortis for a quarter of an hour before dipping; then dip the brass in the same.

Chinese Bronze.-Powder and make into thin paste with vinegar, vermilion, 2 oz.; verdigris, 2 oz.; alum, 7 oz.; sal ammoniac, 5 oz.; after using, gently warm the article; afterwards wash and dry, and repeat the process until the required tint is obtained. By adding a little blue vitriol to this mixture a chestnut brown is obtained, and a little borax gives a yellow tint.

Lacquering. This process is varnishing metals to protect their colour. The work is first thoroughly cleaned, and then pickled for two hours in a pickling solution of 3 parts water and 1 part nitric acid, contained in an earthenware vessel, and afterwards scoured with fine sand and water, applied with a brush.

Dipping Brass.-After pickling, the work is dipped for 3 seconds in pure nitric acid, and afterwards instantly plunged into a solution of whiting and water, or of water and common washing soda, which removes the acid, and the work comes out a fine gold colour; next dry and lacquer. The work should be held with tongs made of brass, when dipping. The lacquer to be warmed and applied with a camel's hair brush to the work, which should be previously heated to 212°.

Dissolving Metals.-Copper, bismuth, nickel and zinc, dissolve in nitric acid. Lead and antimony, dissolve in a solution of nitric acid, I part; hot water, 2 parts. Tin dissolves in hydrochloric acid.

To remove lacquer from brass, boil for 20 minutes in a solution of water, 1 gallon; potash, lb.; withdraw and plunge into cold water.

Silvering Brass, Iron, and other Metals.-First clean and pickle the articles in the same way as for tinning, as given above, then immerse them for a few seconds in a solution of cyanide of silver. Another process is: heat 1 oz. nitric acid until it boils, then add a few pieces of silver; as soon as they are dissolved add a handful of common salt to kill the acid, then make it into a paste with whiting, and apply with water and wash leather. Another process is: mix 1 part of dry chloride of silver, finely powdered, with 3 parts of pearl ash, 1 part of chalk, and 1 parts common salt; rub on with water and wash leather.

Gilding Brass, Bronze, and Other Metals.-Apply the following mixture at boiling heat:-cyanide of potass, 2 lb.; carbonate of potass, 5 oz.; cyanate of potass, 2 oz.; the whole diluted in 5 pints of water, containing in solution oz. chloride of gold; and afterwards varnish the gilt surface.

To Whiten Silver.-Boil in a solution of:-1 part cream of tartar; 2 parts common salt, and 50 parts water.

To Dead-Whiten Silver.-Boil in a solution of alum and water until the desired tint is obtained, and wash well with a brush in hot water with soap and carbonate of soda.

Silver Paint.-Gum lac is dissolved in 4 times its volume of alcohol, and to this thick solution, silver powder is added, in the proportion of I part powder to 3 of the solution. The surface to be coated, is covered with spanish white, the metallic mixture is applied with a brush, and when dry, is burnished with a steel or stone burnisher. Bronze gold, or any other metal powder, may be used in the same way.

Whitening Brass.—Make a mixture of 2 lbs. grain tin, 1 lb. cream of tartar, and 1 gallon of water; boil and immerse the brass for a few minutes at a boiling temperature.

Frosting Silver.-Apply with a brush, a solution of water half a pint; cyanide of potassium, 1 ounce.

Lacquer Varnish for Colouring Metals.-Mix turmeric and annatto, with lac varnish, to the required depth of colour.

Zinking, or Coating Small Articles with Zinc.-First clean and pickle, next dip the articles in a mixture of zinc dissolved in hydrochloric acid, to which a little sal ammoniac is added; then dry and dip in melted zinc and shake off the superfluous metal.

Coppering or Bronzing Iron and Steel Articles.-Clean and immerse in a solution of sulphate of copper, 3 oz.; sulphuric acid, 31⁄2 oz.; water, I gallon.

Tinning Iron and Steel.-Clean and immerse in hot oil or tallow, and then immediately dip into melted tin.

Moire Metal.-Clean and heat the tin over a clear fire, until water will fizz on its surface; then dip it quickly into a mixture of-water, 4 parts; muriatic acid, I part; nitric acid, 1 part; rinse in water, dry quickly in hot sawdust, and varnish while hot.

HARDENING, SOFTENING, AND TEMPERING PROCESSES. Case-hardening Wrought-Iron.-Pack the articles to be hardened, in a box, filled to the top with small pieces of bone and wood charcoal, and a few pieces of burnt leather, the heaviest articles to be placed at the bottom of the box. Make the lid of the box tight, with a lute of equal parts of clay and sand. Subject for 10 hours to a red heat in a furnace, and quench the articles in water. NOTE.-Articles to be case-hardened before placing in the box, should have the threads of screws and nuts, and other parts which require to be left soft, plugged with clay.

Hardening Wrought-Iron with Potash.-This process only hardens to a very slight depth. Heat the article to a bright red, rub the surface well over with powdered prussiate of potash, or with a mixture of 3 of prussiate of potash, to 1 of sal ammoniac reduced to powder, and allow it to cool to a dull red, then quench in water. By repeating the process, a slightly deeper hardening will be obtained, but it is much inferior to casehardening.

To harden Malleable Cast-Iron. Heat the article to a bright red, rub the surface well over with a mixture of equal parts of potash, saltpetre, and sulphate of zinc, allow it to cool to a dull red, and quench in water. To harden Cast-Iron.-Heat the article to a bright red, and quench in a mixture of 3 gallons of water, pint oil of vitriol, and 2 oz. saltpetre.

Another mixture for quenching consists of salt water 10 gallons, salt I peck, oil of vitriol pint, saltpetre lb., prussiate of potash lb., cyanide of potash lb,; by repeating the process cast-iron may be made harder.

To harden Cast-Iron.-Another process is to heat to bright red, and

rub the surfaces with a mixture of equal parts powdered prussiate of potash, saltpetre and sal ammoniac. Allow the article to cool to red heat and quench in a mixture-4 oz. sal-ammoniac and 2 oz. prussiate of potash per gallon of water.

To anneal or soften Finished Iron or Steel Work.-Lute an iron box with clay, and place the articles in the box, full of turnings or borings, of the same metal as the articles are made of. Make the lid of the box tight with a lute of clay. Heat slowly to a red heat in a furnace, and let the fire die out.

To soften Steel Forgings, &c.-Heat to a low red heat, and cool in lime or whiting.

To soften Steel Forgings, or Hard Steel or Iron.-Another process is to pack the articles in a box full of whiting or iron borings, make the lid of the box tight with a lute of clay, heat to a low red heat in a furnace for 4 hours and let the fire die out.

To drill Hard Steel.-Heat the drill in a charcoal fire, and quench in mercury. Moisten the work when drilling with a mixture of turpentine and camphor.

To soften Chilled Cast-Iron.-Heat the article to nearly white heat, and cover it with a good depth of small coal, and let it remain until cold.

To soften small Castings of hard Cast-Iron.-Pack them in a box of fine coke screenings, put a thin layer of fine sand on the top well damped, heat in a furnace to a low red heat and let the fire die out; or they may be softened to a slight depth by steeping for 24 hours in part aqua fortis to 4 parts of water.

Malleable Cast-Iron.—The articles are first cast in cast iron, and malleableised, by burning off the carbon combined with the iron from which the castings were made,—by a process of annealing. The iron used is a white hematite metal, No. 5 brand, which contains little carbon. The castings are first cleaned, and then packed into iron boxes, with alternate layers of either fine iron scales from rolling mills, or powdered hematite The boxes are closed at the top with a mixture of sand and clay, and are next placed in an annealing oven, where they are kept under an equable red heat for from 7 to 14 days if the castings are light, and for about 21 days if they are heavy.

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Welding Cast-Steel.-Mix borax 10 parts, sal ammoniac 1. Simmer over fire for 1 hour, or until clear, pour out, cool, and reduce to powder. Heat the steel in a coke fire, to bright yellow heat.

Welding Cast-Steel.-Another mixture is, powdered limestone 6 parts, sulphur part; and another mixture is, borax 10 parts, sal-ammoniac 2, sulphur i part.

Restoring slightly burnt Cast-Steel.-Borax, 1 lb.; sal-ammoniac, lb.; prussiate of potash, lb.; resin, 1 oz.; powder and mix with 1 gill each of water and alcohol. Boil for a short time to a paste, dip the hot steel in the mixture, and slightly hammer.