This section is from the book "English Furniture", by Frederick S. Robinson. Also available from Amazon: English Furniture.
Another is that with the introduction of mahogany it , was possible to make finer and stronger joints, the former comparative looseness of which necessitated in the Stuart chairs those numerous cross-rails with which we are familiar.1
This banishment of the turned rail seems to mark a more radical difference between the Stuart and later chairs than does the appearance of the cabriole leg. At any rate it is a more sudden development than the introduction of the latter. If we consider the form of the cabriole leg, there are the elements of it to be found in those chairs with convex and concave curves which I have already described. Place a convex curve above a concave one, smooth away the point of junction, and the cabriole leg at once appears. After all, it turns out to be merely a simplification of more elaborate shapes based upon sculpture. The terminal figures of Italian console-tables and French commodes simply disguise the two simple curves which in England, as a rule, take their place. This was due in part to a lack of sculptural talent, to a greater simplicity in our insular taste, and to the nature of the new wood, mahogany, which does not lend itself easily to carving in very high relief. Grinling Gibbons had no great successor, and if one had appeared he could not have done in mahogany what Gibbons did in lime-tree. Nevertheless we can point to not a few creditably carved lions' heads and human faces upon mahogany furniture (cf. Plate lxxxvii.i).

Plate LXXXVII.
I - Settee, Walnut Veneer Or Walnut Early 18th Century
2 - ,, „ 1st Half 18th Century
3 ≫&Raquo; " " "
LXXXVII. (1) Settee, walnut veneer and walnut. Early eighteenth century. With lion masks, en suite with lxxxv. (2). Messrs. Partridge. (2) Settee, walnut. First half of eighteenth century. The back is inlaid with vases of flowers. V. & A. M.
Dimensions: Height 42, Length 52 inches.
(3) Settee, walnut, veneered. First half of eighteenth century. V. & A. M.
Dimensions : Height 42¼, Length 50¼.
Besides the lack of sculptors of high merit there is another influence to be considered, which was in part the cause of the decline of carving in relief. This is the wider use of inlay due to the importation of exotic coloured woods. A flatter field is required for the application of inlay, and a more open one than was afforded in furniture carved in high relief. To this again we may attribute the restricted use of turned work, and the disappearance of the pierced and carved open-work backs of the late Stuart period. The decay of sculpture, then, and the increased use of inlay, may both be regarded as in part responsible for the discarding of the turned upright and for the introduction of the cabriole leg which follows. There can be but one change from the round, namely, to the flat or comparatively flat, and thus we find evolved the flat-shaped uprights and the flat spoon-backs of the William and Anne chairs.
1 A third inference might be that a sitter's feet now rested on a tolerably clean floor.

Plate CXXIV. Commode, Mahogany Veneered And Inlaid
CXXIV. Commode, mahogany, veneered and inlaid. Augustus Spencer, Esq.
William's name renders it unnecessary to look far for the foreign influence which introduced this change. As the Dutch were chiefly instrumental in the importation of foreign woods and the profuse employment of inlay - inlaid chairs being with them a speciality - to the Dutch must be assigned the chief credit of imposing that new style which was to reach its culmination of grace in the mahogany period.
What, then, are the main characteristics of the new style? In the first place, as might be expected from the continuous tendency to strive at lightness, the back is much more open than that of its Stuart precursor. The un-upholstered chair's back may be said to consist invariably of three parts: the two uprights and the splat, or central portion, which supports the sitter's back. These parts are much less adorned, especially in chairs of a not elaborate kind, than is the case with those of the late Stuart period. Even in fine chairs with much carving on the splat the uprights are often very plain. These plain surfaces by no means detract from the artistic merit of the chairs. A suggestion of poverty in them is partly counterbalanced by the fact that, just as the cabriole leg with its curves induces a play of light upon its plain surfaces, the back of these chairs when observed from the side is seen to be curved to match, and reflects the light with great variety of tone. At the top of the back there is a convex curve to fit the nape of the sitter's neck. This becomes a concave to receive his shoulders, and comes forward again to a convex curve to support the small of his back. The utterly rigid perpendicularity of the old oak chair and its Stuart successor has disappeared.
Instead we find the beginnings of a consideration of human anatomy. Arm-chairs are not too common, and where arms are used they have ceased to be ended with the acanthus-leaf.
 
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