Sterro-metal varies in composition as shown in the Table p. 350.

This alloy has great tensile strength, and may be used instead of wrought iron.

Babbit's Metal is used for bearings of machinery. It is very soft, wears smooth, and reduces friction. If the journal becomes heated, the alloy melts.

White Brass is a name given to various alloys used for bearings, and intended to work smooth. These are made of various composition besides those given in the Table.

Pewter should consist of 4 or 5 parts of tin and one of lead.

It is used for drinking cups and other purposes, also sometimes for covering counters where liquor is sold.

It should be remembered, however, that cheap pewter generally contains an excess of lead, and in that case is apt to poison any liquid in contact with it.

Pewter consisting of 4 tin and 1 lead "has the specific gravity 7.8, so that specimens having a higher specific gravity than this will be known to contain more lead." 1

Solder is the name given to several different alloys used for the purposes of making joints between pieces of metal.

The effect is not merely mechanical, for the solder itself combines with the metal to be united, and forms a fresh alloy.

The composition of the solder used in connection with the different metals varies immensely; and the proportions in which each different kind of solder is mixed also varies according to circumstances.

Every solder must be more fusible than the metals it is intended to unite.

Hard Solders are those which fuse only at a red heat, and which can be therefore used only to metals which will endure that temperature.

Soft Solders melt at very low degrees of heat, and may be used for nearly all the metals.

The more nearly the solder agrees with the metal in hardness and malleability, the stronger will be the joint.

Thus brass or copper united with soft solder could not be hammered without breaking the joint, whereas a joint in lead or tin, made with soft solder, can be safely hammered.