The department of the carpenter is distinguished from. that of the joiner, in that it regards the substantial parts of the edifice, such as the framing of roofs and partitions, and, in fact, all that contributes to the solidity and strength of a building; while that of the joiner is more particularly directed to the convenience and ornamental parts: it is hence evident that the carpenter should be well acquainted with the strength and stress of the materials he uses, which are for the most part in great masses; hence he should be careful not to overload his work with timber of greater magnitude than is absolutely necessary, though at the same time he should study economy in their use; he should also be able to ascertain the dimensions necessary, without weakening the building, and endeavour, by steering a mean course, to produce the maximum of strength, without overloading the several parts of his frames with too much timber; or, by putting too little, endanger the safety of the whole fabric. Thus the art of carpentry depends greatly on these two considerations, viz. the strength of the materials, and the stress or strains they are subject to; these strains may be thus - first, laterally, as when a tenon breaks off, or a rafter gives way close to the wall; secondly, the strain may be in its length, when it is drawn down or pushed in its length as a king post, where the strain tends to separate the fibre of the wood by pulling; hence, knowing the strength of the timber to resist such efforts, we are enabled to calculate the dimension necessary to be given it, to resist the probable stress it may have to overcome; all tie-beams are subject to this strain: thirdly, the strain may act by pressure, or the timbers may be compressed in length; this is the case with all pillars, posts, or struts; and in this case, according to the length of the post, etc, it must be of a sufficient diameter to resist the weight which it has to support. Strains are often compound, as a joist or lintel when placed horizontal, or obliquely as in a rafter; or many of those strains may be combined, as in circular or crooked work. All these things are to be particularly attended to.

The various kinds of timber used amongst carpenters ire as follow: - Oak, fir, elm, ash, chesnut, and beech. A few observations on each will, perhaps, guide him in his selection to appropriate those to the several parts of a building to which they are best adapted; and, first, of Oak : - It is not necessary here to describe this timber, as every carpenter must be acquainted with it; we shall, therefore, only observe, that it is the most ponderous, as well as the hardest grain and firmest texture of any timber used in building; but from its great weight, and difficulty of working, it is but rarely used, except where very great strength is required. In selecting it, however, we should be careful that it is well-seasoned, as it is very apt to warp or cast; and the workman should be careful not to let any of the sappy parts be used, as they soon decay, and consequently are unfit for the purposes where this timber is required. The next in order is Fir, and this is the most generally useful of any timber for buildings, as we can procure scantlings of much greater dimensions than any other, and it has many advantages, as with a considerable degree of strength it combines a lightness or texture that is highly advantageous; and, also, that it is not subject to cast so much as most other timbers; it possesses a considerable degree of elasticity, and will bend a great deal before its strength becomes perceptibly impaired, consequently very proper for framing of roofs, floorings, etc. and the grain in general runs straight, and where it is sheltered from the vicissitudes of wet and dry, or protected from the weather, it will last a very considerable time; but for those parts of a building that are exposed to the weather, as window frames or cills, door posts, or any other part where the rain has access, oak is by far the best material, and will endure much longer than any other timber; and for piles, and such like, that are constantly under water, it in time gets as hard as ebony, and becomes in appearance like ebony itself; a striking instance of which, we have in those piles called Conway stakes, driven into the bed of the Thames, near Chertsey, in Surrey, supposed in the time of Julius Cæsar, which are of sufficient hardness to be used for purposes to which ebony and other hard woods are applied, such as the stocks and blades of squares, and the heads of gauges. Elm is a wood but little used in building, being so very liable to twist and warp; it is chiefly used as weather boarding for barns, etc, and in that situation it is found to resist, (perhaps as well, or better, than any other wood,) the alternate heats of the summer sun, and the rains of a wet winter, particularly when coated with common paint or other composition.

Ash is a very tough wood, but little used in building, more, perhaps, from the demand among wheelrights and millwrights, than from any inferiority to many other woods, as it is not very subject to warp, and is very elastic and tough, as well as of, in general, a straight and even grain.

Chesnut is a wood scarcely inferior to oak for many purposes, being extremely durable, and not subject to decay, of generally an even grain and free from knots or curls, very tough, and of dimensions sufficient for most purposes of carpentry. Beams that have been taken from old buildings of more than a century standing, have been found as sound, and perhaps harder than when first placed in their original situation, and some posts that have formed a part of the same building, which have been always exposed to the different degrees of wet and dry, seemed little or nothing the worse, and, to appearance, as sound as when first the building was erected.

Beech is the last wood I shall here notice: it possesses qualities that recommend it for strength, evenness of grain, and toughness; it is not surpassed by any other English timber; but if exposed to the action of the atmosphere, it is not found to stand so well as many other woods; it is, however, particularly applicable to sweep work, and is on that account much used by millwrights, and might be used to many purposes of building with considerable advantage; it is also particularly adapted for pins in framing and doweling boards together, as it is not brittle or liable to snap, and drives well.