Having determined on the outline of a chair back it is necessary to study its composition, that is, to decide how the space within the outline is to be treated. This question is sometimes decided before the design is begun, as, for instance, when it is panelled, or upholstered. If, however, it is to be of some other pattern, study is necessary. Aside from the methods just mentioned, the back may be filled with slats arranged in one of the four ways shown on Plate X.

A single broad slat ("splat") may be placed in the middle of the back between the top and the seat rail, or it may stop on a horizontal rail just above the seat. Such a slat can be treated as desired either with figured veneers, inlay, painting, carving, perforations, etc. A back composed of a number of vertical turned or half turned slats filling the space has been called a "banister back." But the slats are not always turned, they are sometimes flat, moulded, perforated, in-laid or carved. They are sometimes placed horizontally and bowed, the concave side toward the seat. The curvature increases as the slats approach the top; so, though the lower slat may be nearly straight, the top one is hollowed considerably to receive the shoulders of a person sitting in the chair. This gradual change in the curvature of the slats is sometimes substituted for the sloping of the back posts.

Chairs made with turned posts and having horizontal slats in the back were named by the number of slats. As, three backed, or four backed chairs; that is, three or four horizontal slats. Five backed chairs were quite uncommon.

It is perhaps almost unnecessary to say that both horizontal and vertical slats may be used in the same back. There is an endless variety of ways in which these slats and balusters may be grouped, spaced, and proportioned to fill the space well. Whether the slats or the spaces shall be the broadest ? What is the best outline for the balusters? Are the kind of questions the designer is to ask himself, striving always to obtain the beautiful rather than the eccentric and curious forms.

The outline of the top rail of the "rectangular" and "trapezoidal" backs has its influence on the appearance of the chair, and it may be more or less ornamented. Four forms are shown on Plate X. which explain themselves.

In Plate VIII. are shown five plans of arm chairs. One of these has the arm straight, following the plan of the seat. Two of the others indicate how the space between the arms is made wider than the seat at the back by curving the arm; the front post remaining in the same position as in the first plan. The plans drawn beneath the chair with the "receding arm post" show how the arm may be a compound curve or a continuation of the curve of the back. In the former not only does the curve give a maximum width between the arms, but it also permits of the front scroll of the arm turning out, thus preventing the chair from seeming narrow.

In some chairs the plan of the arm follows the curve of the back so there is no angle where the two join. This is illustrated in the plan of a "Windsor" chair, where the piece from which the arm is cut is continuous from one side of the chair to the other, the slats of the back passing directly through it.

Chair arms may be horizontal or they may slope to a greater or less degree with the highest point where they join the back. Stretchers are used to strengthen the chair. The legs when braced by them are more firm and less likely to loosen at the seat frame joint. Plate VIII. gives the plans of three arrangements of stretchers. When placed high enough to be out of the way of the feet of a person using the chair the stretcher may form a trapezoid parallel to the seat frame; or if the chair seat is high and a foot rest is desired the stretcher may be arranged this way and set low for the purpose. In olden times European chairs were always made high and with a foot rest, that a person might keep his feet off of the cold floors. Now that it is not necessary to keep the feet away from the floor, it is not customary to allow them to touch the stretchers of chairs. These are, therefore, arranged diagonally between the legs of the chair; or, the front and back legs are joined together by rails, while a third unites the two side rails. This third rail may be set in any position, but frequently it is a little nearer the front than the back.

One of the most difficult tasks the furniture draughtsman has is to design and lay out for the shop the drawing of a chair that will be satisfactory. No drawing is more deceptive than the full size for a chair, and it is by experience only that a draughtsman can judge what will result from the working drawing. Most draughtsmen of considerable experience, when working out a detail, endeavor to have before them a chair somewhat similar to the one they are drawing.

A good chair should first of all be comfortable to sit in. If intended for general service it ought not to be too heavy to move about easily, and it should be well proportioned.

In planning the seat determine its height above the floor, its width at the front, its width at the back, and the depth from front to back. These vary as desired, and what will make a satisfactory chair for one person, may be quite unsuited to another; consequently there are all sorts and sizes of chairs. It is, however, desirable to have a starting point from which to reckon, and experience has fixed a chair seat eighteen inches above the floor as proper, no conditions being given. If it is less than this it is considered low, and if more it is high. The purpose for which a chair is to be used also serves as a guide for dimensions. If intended for use at a writing table eighteen inches will be satisfactory; if for a dining chair eighteen and a half, or nineteen inches is not too high. Occasionally as high as twenty inches may be used. When the chair is not to be used at a table, seventeen and a half, or seventeen inches high is satisfactory for most purposes.