Mix 10 parts of fine iron filings, 30 parts of plaster of Paris, and one-half parts of sal ammoniac, with weak vinegar. Work this mixture into a paste, and apply quickly.

Cement for Steam Boilers. Four parts of red or white lead mixed in oil, and 3 parts of iron borings, make a good soft cement for this purpose.

Cement for Leaky Boilers. Mix 1 part of powdered litharge, 1 part of fine sand, and one-half part of slacked lime with linseed oil, and apply quickly as possible.

To keep plaster of Paris from setting too quickly. Sift the plaster into the water, allowing it to soak up the water without stirring, which would admit the air, and cause the plaster to set very quickly. If it is desired to keep the plaster soft for a much longer period, as is necessary for some kinds of work, add to every quart of water one-half teaspoonful of common cooking soda. This will gain all the time that is needed.

To keep paste from spoiling. Add a few drops of oil of clove.

To make a cement that will hold when all others fail. Melt over a slow fire equal parts of rubber and pitch. When wishing to use it, melt and spread it on a strip of strong cotton cloth.

Bath for cleaning sheet copper that is to be tinned. Pour into water sulphuric acid, until the temperature rises to about blood heat, when it will be about right for pickling purposes.