Case Hardening Mixtures.—Three parts of prussiate of potash, one part sal ammoniac; or, one part of prussiate of potash, two parts sal ammoniac and two parts bone dust.
Glue to Resist Moisture.—One pound of glue, melted in two quarts of skim-milk.
Marine Glue.—One part of India rubber, twelve parts mineral naphtha or coal tar. Heat gently, mix, and add twenty parts of powdered shellac. Pour out on a slab to cool. Heat to about 250 degrees and it is ready for use.
Glue Cement to Resist Moisture.—One part glue, one part black rosin, ¼ part red ochre, mixed with the least possible quantity of water; or, four parts of glue; or, one part oxide of iron, one part of boiled oil (by weight).
BABBITTING BOXES.
When the babbitt in a box is badly worn, and needs re-babbitting, remove the cap, take out the shaft and chip all the old babbitt out of both box and cap; then replace the shaft in the box, and line it up perfectly level and square by putting liners in between the shaft and the edges of the box; then put stiff putty around the shaft and against the box at both ends, to prevent the babbitt from running out; then heat the babbitt metal until it runs freely, and pour it into the box until it is full; then put on the cap, and place about the same amount of liners between its ends and the top of the shaft as was put under the shaft, with long liners of sheet iron or tin extending from one end to the other of the box, parallel with and on both sides of the shaft; then put putty around the shaft and against the cap at both ends; heat the metal again, and pour it in through the oil hole. After it is cool, remove the cap and liners, drill out the oil hole and replace the cap, being careful to put just enough liners under it so that the box will be tight and still have the shaft run cool.
COMPOUND ENGINES.
The Compound Engine dates from the year 1781, when Hornblower, a contemporary of Watt, conceived the idea of utilizing the force in the exhaust steam of the simple engine in a second cylinder.
From his crude design, the constant progress of experiment has developed the marvelous engines now used in ocean steamers, and in both large and small power plants, also on locomotives. Some of the compound engines built in the early part of the century show results, according to the records, not far behind the best attainable in modern times.