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Alloys (Knife cut the size)

knife cut the size of the required piece on the sil- | times, been generally used in the formation of vering of another glass; a small globule of mercury (the size of a pin's head for a surface the size of the finger nail) is dropped upon the cut piece.

The mercury penetrates as far as the cut, and al- Specula of Telescopes. busts, medals and statues.

Melt 7 lbs. of copper, and when fused add 3 bs. of zinc and 4 lbs. of tin. These metals will comlows the piece to be removed. It is then gently bine to form a beautiful alloy of great lustre, and pressed on the spot with a piece of cotton.

Bath-metal. of a light yellow color, fitted to be made into specula for telescopes. Mr. Mudge used only Melt together 1 lb. of brass and 44 oz. of spelter. copper and grain tin, in the proportion of 2 lbs. Brass.

Put 4 lbs. of copper into a crucible, expose it to heat in a furnace, and when perfectly fused add 1½ lbs. of zinc. The metals will combine, forming that generally used alloy called brass.

Another. For brass which is to be cast into plates, from which pans and kettles are to be made, and wire is to be drawn, braziers use calamine of the finest sort instead of pure zinc, and in a greater proportion than when common brass is made; generally 56 lbs. of calamine to 34 lbs. of copper. Old brass, which has frequently been exposed to the action of the fire, when mixed with the copper and calamine, renders the brass far more ductile and fitter for the making of fine wire than it would be without it.

Pinchbeck.

Put into a crucible 5 oz. of pure copper; when it is in a state of fusion add 1 oz. of zinc. These metals combine, forming an alloy not unlike jeweller's gold; pour it into a mould of any shape. This alloy is used for inferior jewellery.

Some use only half this quantity of zinc, in which proportion the alloy is more easily worked, especially in the making of jewellery.