These extreme sizes are now very seldom used, except in the case of large dress or state carriages and coaches. The form of wheel now generally preferred in practice is of the dished or conical kind, and the axle-arm on which it revolves is sloped or bent so far out of the horizontal that the lower spokes are in a vertical position. Undoubtedly the friction is increased by this arrangement, because a wheel on a horizontal axle runs easiest and smoothest; and when the axle-arm is slanted downwards towards the point the wheel has a tendency to bind harder against the shoulder which butts against the nave of the wheel, and the friction between the two is greater than would be the case if the axle-arm were perfectly horizontal. This, however, is a very small objection, inasmuch as this collar is firm and strong, and well fitted to bear any strain that may be thrown on it by the wheel; whereas, if the force acted in the other direction, or against the nuts and linch-pins, there are very few that would last out a day’s journey. The advantage of throwing the strain on the firm and strong shoulder, which is well able to withstand it, is evident; and in this case, in the event of the nuts or linch-pins falling off or giving way, there is not so much danger of the wheel coming off at the moment the nuts go, as its tendency when on a level road is to run upwards towards the shoulder. Besides this, as the lower spokes are in a vertical position, the upper ones spread considerably outwards, and thus afford a greater space for the body between the wheels without the track on the ground being increased; and another advantage is that the mud collected by these conical wheels is thrown off away from the carriage. The hind wheels of an ordinary carriage vary from 4 feet 3 inches to 4 feet 8 inches; the fore wheels are from 3 feet 4 inches to 3 feet 8 inches. The number of felloes in each circumference varies according to the number of spokes, two spokes being driven into each felloe; 14 to 20 spokes are a usual number for a hind wheel, 12 to 18 for a fore wheel; however, there is no rule to guide one in the matter, experience being the only teacher. The wheels should be made with a due regard to the offices they have to fulfil; but we are inclined to think that this branch of the trade has not received that careful study which it deserves. Coachmakers seem in such a hurry to produce a perfect vehicle all at once, instead of beginning by improving the parts and then applying these improvements to the whole. [Illustration: Fig. 11.] The mode of constructing a wheel is as follows:—