The timbers that are to be used should be well and carefully selected. The nave or stock, which is sliced from the limb of a tree, should be as nearly as possible the size required in its natural growth, so that it will require little reduction beyond what it receives in the lathe in bringing it up to the true circular form. The reason of this is that the annual rings which mark the grain of the timber should be as little disturbed as possible, as they are not all of equal strength and durability, the outer rings being pretty strong, but as they get nearer to the centre the wood is much softer. If, then, this outer hard casing is cut away, even only in part, it is signing the death-warrant of the poor nave, for the interior parts of the timber are not nearly so capable of resisting the destructive influences around, and in a very short time they will become completely soft and rotten. [Illustration: Fig. 12.] As already remarked, the spokes should be cleft, not cut. The felloes which form the outer periphery of the wheel should also be cut as closely following the grain as possible. When the wheelwright has carefully selected his timbers, he commences work by turning the stock in the lathe to the size required. Then he marks with a gauge of the same width as the spokes 4 circles as shown at _a_ _a_ _a_ _a_, Fig. 13. The first and third of these mark the position of the front or face spoke, and the second and fourth mark the position of the back spoke. Two holes are then bored in each mortise in succession, after which they are squared out with proper chisels. Truth of eye and skill of hand are the workmen’s only guide in this operation, though it is evident that it is the most important operation of the whole, as upon it depend the accuracy and solidity of the wheel when finished. The tenons of the spokes are then cut to fit the mortises, parallel in their thickness, but in width they are cut slightly taper-wise, _i.e._ the extremity of the tenon is made about the same size as the mortise, but at the shoulder it is about one sixteenth of an inch larger, so as to make sure of the tenon filling the mortise when driven home. [Illustration: Fig. 13.] Before cutting the mortises the stock should be fixed at some convenient angle, regulated by the amount of dish it is intended to give the wheel. This is particularly necessary, or when the felloes come to be fitted, if the mortise-cutting has been done in a slovenly way, the dish will not exist at all, or if it does it will be in the wrong direction.