The sides, A, B, and C, are now supposed to be finished; it therefore only remains to operate on D to complete the work. The edge or fourth side, D, might be planed at right angles to the first side, A, by the assistance of the square, if it were not required to be also parallel to the second side, B.

We made A and C parallel to each other; the same relation must therefore exist between B and D, to render the work correct. The marking-gauge must be set to the new measure, the width or distance required between the edges - the head being rubbed against B, while the point marks out the new surface, D. Two lines must be scored - one on A, the other on C - to guide us in planing the edge square to them.

If the work has been properly executed, the sides will prove equally true when tried by the square in any direction. Sometimes the several surfaces will appear true in the order of their formation, but on reversing the test they will no longer agree. This want of accuracy can occasionally be traced to the square, which may not be in good order, but more frequently the fault rests with the workman.

Squaring and planing-up works are not easy of accomplishment, and even the simplest works require considerable skill to achieve satisfactorily, and constant practice is necessary to insure success.

We must suppose our pupils to have only commenced their apprenticeship, and shall therefore begin with the mere rudiments of the joiner's art.

The construction of a plain deal box is probably the simplest work our pupils could select for their first attempt. The wood for the "carcase" of the box having been cut out and planed in accordance with the directions already given, the sides may now be glued or nailed together. Before detailing the method of "glueing up" works, however, a few words respecting the choice of the glue may be useful to our readers.

The best glue is prepared from parings of the hides of animals, previously to the process of tanning. The quality of the glue may be tested in several ways. The superior kinds are of a pale brown colour, and devoid of taste or smell. When held between the eye and the light the cake of glue should appear semi-transparent, and entirely free from cloudy or black spots, which indicate the presence of foreign matter. If a large quantity of glue is to be purchased, it will be advisable to take a sample, and subject it to a severe trial. The glue must be broken into small pieces, and placed in a vessel with sufficient cold water to cover it. If, after the lapse of three or four days, the glue swell powerfully without melting, it may be considered the best quality.

In dry weather a cake of glue is generally crisp and hard, but it is liable to become soft in a moist atmosphere. If the glue be soft in dry weather it should be rejected, being probably of inferior quality.

The kettle in which the glue is melted for use consists of two vessels, one within the other, a certain space existing between them for a water-bath to determine the temperature, which can never exceed that of boiling water. This provision is absolutely necessary to save the glue from being unduly heated or burnt, whereby its adhesive properties would be destroyed.

It is a good plan to allow the glue to soak in cold water for several hours before placing the kettle on the fire. The kettle must not be put on a fierce fire, but should be suffered to simmer gently on the hob, until the glue is thoroughly melted. A cover should be provided to exclude the dust, a notch being made in the edge for a stick or brush, with which the glue may be occasionally stirred. If too thick, a little of the hot water contained in the larger vessel may be added to the glue, which should be sufficiently thin to run in a fine stream from the brush. Shortly before removing the kettle the water may be allowed to boil gently, to ensure the glue being of sufficiently high temperature to remain fluid until the neighbouring portions of the work to be united are. properly adjusted. The strength of common glue may be somewhat increased by adding a small portion of finely-powdered chalk, which must be thoroughly incorporated with it. Another preparation which will resist moisture is made by melting one pound of the best glue in two quarts of skimmed milk.

A very strong glue of great service for uniting small mouldings and other separate portions of work which are liable, owing to their small surface, to become detached from the main body, may be made thus: - Dissolve one ounce of the best isinglass, by gentle heat, in a pint of water, and strain it through a piece of cloth. The isinglass must now be placed in a glue-kettle with the best cake glue, which has been soaking for twenty-four hours in cold water. A gill of the strongest vinegar must be added, and the whole allowed to melt slowly near the fire. The mixture must be stirred occasionally to ensure the complete incorporation of the ingredients. The glue may be suffered to boil up once, after which the impurities must be strained off, and the cement left to cool. If the kettle be wanted for ordinary glue, the "strong glue" may be poured on a slab of stone to cool, after which the cake so formed can be broken into pieces of a convenient size for use.

Having ascertained that the four pieces of which the "carcase" of the box is to be constructed are quite square, and fit truly to each other, they must be marked, so that their proper relationship may be known when "glueing up" is commenced.

To ensure a good and firm joint it is necessary to have the glue very fluid, and as hot as the water-bath of the kettle can make it. It is also of equal importance to bring the pieces which are to be united as nearly in contact as possible, thereby excluding the superabundant cement which would otherwise prevent the close union of the parts.

If the top of the bench be uneven a flat board should be placed on it, otherwise some difficulty may be experienced in glueing the box together truly square. One of the sides of the "carcase" must be laid on the board with the inner side upwards, and the end pieces, which have respectively been glued on one extremity, are rubbed firmly down on it, in order to exclude the surplus glue and bring the wood into close contact. The opposite extremities of the ends are next glued, and the second side is pressed forcibly upon them.