There is no absolute rule for the dish of the wheel or the pitch of the arm of an axle. Experience and custom point out to a builder what is best for different carriages and different countries. It is sufficient to say that a spoke two feet in length will last longest when not dished more than its own width in its length, and that the pitch of the axle arms, to ensure chiefly the duration of the wheels, should not be more than will leave the spokes pointing towards the ground, not upright, but narrower at the naves than at the rims by three-quarters of an inch when the spokes are two feet long. This rule is simply for the duration of the wheel as long as possible, without reference to any other consideration, which the Coachbuilder, however, may find overrule what I have said. If the axles of a carriage are rather stronger than is necessary--having regard to their length between the shoulders, and the weight they have to carry--it will be found to have a considerable influence upon the carriage, which will follow more steadily and quietly for the additional strength. I do not propose to enter in this series of lectures at any length upon the subject of Springs. I think we are far from having attained perfection either in the manufacture or shape of springs for carriages. It may have been remarked that the first springs were all elbow springs, placed in different positions, for different carriages. A double elbow or horizontal spring of a length of four feet seems to give the most easy play of any shape, and if made nearly straight at first wears little in the course of time compared with the elliptical shape. In perch carriages we have abandoned the nearly upright spring for the =C= spring, chiefly because the =C= spring is of a more elegant shape, and also resists wear better than the elbow or whip spring, which was found to break away from its supports. In elliptical springs the action of the steel plates is precisely contrary to the action in the =C= spring; in both the back plates are similar in shape, but the shorter plates in the =C= spring are on the inner side of the curve, and in the elliptical they are on the outer side of the curve. A careful consideration of the effects of this variation may lead to a new combination which will be more satisfactory in its results. The elliptical springs made by Hobson were doubly compassed, and the same shape may be seen on some of the public omnibuses. A carriage may be hung to be very easy by using double horizontal springs, one under the other. At the Exhibition at Brussels this year (1876) the most easy hand ambulances on wheels were constructed in this manner. In one elliptical spring you do not have the advantage of two horizontal springs, because the ends are in the elliptical spring united, and if a coupling is substituted at the hind end it is found in practice difficult to keep it upright.