limed 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.

Method of making Artificial Whetstones.--Gelatine of good quality is
dissolved in its own weight of water, the operation being conducted in
a dark room. To the solution one and a half per cent. of bichromate
of potash is added, which has previously been dissolved in a little
water. A quantity of very fine emery, equal to nine times the weight
of the gelatine, is [Transcriber's Note: The original text reads
'itimately'] intimately mixed with the gelatine solution.
Pulverized flint may be substituted for emery. The mass is molded into
any desir