This important material in a manual training room is sold usually in three kinds, Scotch, French, and 'Town,' but all are made from the hoofs and hides of oxen and other animal products.

These substances are boiled, strained, melted, re-boiled, and finally, after several operations, cast into hard square cakes of varying thickness.

Scotch glue is the strongest that is made. It is of a reddish-brown colour, but when held up to the light it should be transparent, or nearly so, and of a bright amber colour. The transparency is a sign of good quality, and it is important that no dull, cloudy spots should be apparent.

French glue is made in two thicknesses, one about a quarter inch, and the other about one-eighth inch thick, both being thinner than the best Scotch. It is very transparent, but this increased transparency is more due to the nature of the glue, which is of a light colour, than to the thinness of the sheets.

Town glue is inferior in every way.

There are various reliable modes of testing the quality of glue. If it is wetted and rubbed, good glue will at once become sticky, while a greasy surface may be taken as indication of bad material. There should be very little smell from good glue, but the odour, such as it is, should never be musty or very objectionable.

When glue is used to attach two pieces of wood, the surplus should be squeezed out by continually rubbing the two pieces of wood together. When these have been rubbed together for a certain length of time a 'set,' as it is called, ensues, the jointed wood is then put on one side to dry. Now good glue will not 'set' too quickly, but will dry after 'setting' very soon.

If glue dries in a joint in an hour or two, or takes a very long time to dry - say more than twenty-four hours - it is inferior, and the work done with it will be defective.

In mixing glue as little moisture as may be necessary should be absorbed, and the best method of preparation is as follows: -

Break up enough glue into as small pieces as are reasonably possible, and place it in the inner of the two glue-pots, just covering it with water. Fill the outer pot with cold water and steadily boil. Stir the glue constantly while it is melting, and when it is thin enough to run off the brush in a steady stream without breaking into drops it is 'made,' and ready for use. Before the glue is quite 'made' a scum of impurities will appear on the surface, and should be removed.

Another way of making glue is to soak it for twelve hours in just sufficient cold water. The glue should not melt by this soaking, but swell considerably; and here is another test of the glue, for the more it swells in soaking the better is its quality, while if it dissolves, it is inferior. The glue and the water in which it has been soaking should now be transferred to the inner glue-pot, and boiled steadily for about an hour.

The first plan, however, is the best for every purpose, though the glue does not keep good so long, and will not bear re-heating so much as in the second method of preparation. Glue loses virtue every time it is heated, and if it gets dirty it is spoiled, so that it is of the utmost importance to keep both glue-pot and glue clean.

Strong Scotch glue is usually considered the best where mere strength is required, but in very fine work, where the dark colour of the glue might show at the joints, French glue is preferable, because of its lighter colour. The very best glue for strength, and the most economical in the end, is a mixture of about equal parts of Scotch and French.