A Useful Hint to Draughtsmen.—­To strain drawing paper on a board, cut the paper to the size required, lay it on the board face downwards and thoroughly wet the surface with a damp sponge or brush, then turn it over and wet the face in the same way; roll it up tightly and let it stay so for five or six minutes, unroll it, and turn up the edges about an inch all around.  Take liquid glue (Jackson’s is the best) and apply it carefully to the edges, then turn them down, and with a paper knife press them to the board all around.  Put the board in an inclined position where it is not too dry or warm, or the paper will dry too fast and tear.  If it is allowed to dry slowly the surface will be perfectly even and smooth, and a pleasure to draw upon.

Joints for Hot Water Pipes.—­Sal-ammoniac, 2 oz.; sublimed sulphur, 1 oz.; cast-iron filings, 1 lb.  Mix in a mortar, and keep the powder dry.  When it is to be used, mix it with twenty times its weight of clean iron filings, and grind the whole in a mortar.  Wet with water until it becomes of convenient consistence.  After a time it becomes as hard and strong as any part of the metal.

When the Process of Galvanizing Iron was First Known.—­A.  The process of coating iron with zinc, or zinc and tin, is a French invention, and was patented in England in 1837.

A Timber Test.—­The soundness of timber may be ascertained by placing the ear close to one end of the log, while another person delivers a succession of smart blows with a hammer or mallet upon the opposite end, when a continuance of the vibrations will indicate to an experienced ear even the degree of soundness.  If only a dull thud meets the ear, the listener may be certain that unsoundness exists.

Useful Hints and Recipes.—­Following is a comparative statement of the toughness of various woods.—­Ash, 100; beech, 85; cedar of Lebanon, 84; larch, 83; sycamore and common walnut, each, 68; occidental plane, 66; oak, hornbeam and Spanish mahogany, each, 62; teak and acacia, each, 58; elm and young chestnut, 52.

An [Transcriber’s Note:  The original text reads ‘ingenius’] ingenious device for stretching emery cloth for use in the workshop consists of a couple of strips of wood about 14 in. long, hinged longitudinally, and of round, half-round, triangular, or any other shape in cross section.  On the inside faces of the wood strips are pointed studs, fitting into holes on the opposite side.  The strip of emery cloth is laid on to one set of the studs, and the file, as it is called, closed, which fixes the strip on one side.  It is then similarly fixed on the other side, and thus constitutes what is called an emery file and which is a handy and convenient arrangement for workshop use.