brittle, while one of copper 39.98 and of tin 65.82 is brittle. An alloy as hard as iron, and not brittle, consists of as high a percentage of copper as 84.68, the proportion of tin being 15:32. Pewter is an alloy of lead and tin, of which the following is the hardest : -lead, 26.03; tin, 73.97: the softest lead, 89.80; tin, 10-20. An alloy much used for lining bushes or journal boxes with, is thus described by the inventor :—

"First melt 4 oz. copper, and while melted add by degrees 12 oz. best quality Bancu tin; then add 8 oz. regulus antimony, then 12 oz. more tin. After the copper is melted, and 4 or 5 lbs. tin have been added, the heat should be reduced to a dull red colour, in order to prevent oxidation; then add the remainder of the metals as above named. In melting the above there should be a small quantity of powdered charcoal upon the surface of the metal. I make the abovenamed composition (which I call hardening) in the first place; then, as I want to use lining metal, add 21 lbs. of Bancu tin to every 1 lb. of hardening. This will produce the metal I now use for lining boxes. I find by experience that this is the best composition I have ever used; so that the proportions for lining metal should be 4 lbs. copper, 8 oz. regulus antimony, and 96 lbs. tin.

"There is economy in first preparing the hardening. There will be less loss by oxidation, as the hardening can be melted at a less temperature than either the copper or antimony separately.

"As there will be some loss by oxidation in using the lining metal, I skim off the oxide and save it. When a quantity is saved, I put it into a crucible with fine charcoal, and expose it to a smart red heat, which will restore it to a metallic state. Add sufficient tin to make it look like the regular lining metal, and use it in lining.

'The box or article to be lined having been cast with a recess for the soft metal, is to be fitted to an iron, formed of the shape and size of the bearing or journal, allowing a little in size for shrinkage; drill a hole for the reception of the soft metal, say from onehalf to three-fourths of an inch diameter. The box having been thus prepared, wash the parts not to be tinned with a clay wash, to prevent the adhesion of the tin; wet the part to be tinned with alcohol, and sprinkle sal-ammoniac upon it; heat the box till a fume arises from the ammonia, and immerse it in a kettle of Bancu tin, care being taken to prevent oxidation. When sufficiently tinned, the box should be soaked in water, to take off any particles of ammonia

that may remain upon it, as the ammonia would cause the metal to blow when poured into the box. Wash the former with fine pipe-clay, and dry it; then heat the box to the melting point of tin, wipe it clean and place it upon the former, and pour in the metal, giving it sufficient head as it cools. The box should then be scoured with fine sand, to take off any dirt that may remain upon it. It is then fit for use."

CHAPTER V.

MISCELLANEOUS NOTES CONNECTED WITH THE

MANIPULATION OF METALS.

(36.) WE take, from a number of sources, a variety of notes and recipes connected with the metals used in construction, which are likely to be of practical use to the reader.

Annealing, Case-hardening, and Tempering of
Iron and Steel.

1. ANNEALING OF METALS." In a considerable number of instances," says the author of the “ Mechanic's Own Book," "bodies which are capable of undergoing ignition, are rendered hard and brittle by sudden cooling. Glass, cast-iron, and steel, are the most remarkably affected by this circumstance,—the inconveniences arising from which are obviated by cooling them very gradually; and this process is called

annealing.' Glass vessels are carried into an oven.

over the great furnace called the leer, where they are permitted to cool in a greater or less time, according to their thickness and bulk. Steel is most effectually annealed by making it red-hot in a charcoal fire, which must completely cover it, and be allowed to go out of its own accord. Cast-iron, which may require to be annealed in too large a quantity to render the expense of charcoal very agreeable, may be heated in a cinder fire, which must completely envelope and defend the pieces from the air till they are cold. The fire need not be urged so as to produce more than a red heat; a little beyond this, bars and thin pieces would bend, if destitute of a solid support, and would even be melted without any vehement degree of heat. If it be required to anneal a number of pieces expeditiously, and the fire is not large enough to take more than one or two of them at once, or if it be thought hazardous to leave the fire to itself, from an apprehension that the heat might increase too much, the following scheme may be adopted :-Heat as many of the pieces at once as may be convenient, and, as soon as they are red-hot, bury them in the dry sawdust. Cast-iron, when annealed, is less liable to warp by a subsequent partial exposure to moderate degrees of heat than that which, has not undergone this operation.