The coach-builders of the future will look to steam and hand machinery as their great assistance in cheapening the cost of first-rate carriages, in multiplying them for the probable increased demand, and also to build carriages more speedily. It now takes from two to three months to build a brougham, of which at least five weeks are consumed simply in the wood and ironwork, a period which by the use of machinery might easily be shortened. There has been much controversy about difference in the length of the front and hind axletree. It has been usual to make no greater difference than will allow the higher wheel to follow in the same track as the lower wheel. In France, however, it has been the practice since the year 1846 to make the front axletree of broughams 6 inches shorter than the hind ones. The object has been to allow the front wheel to be placed nearer to the body. As the front wheel of a brougham must turn entirely in front of the body, the additional gain of 3 inches was very desirable. Some English coach-builders have followed the example of the French. There is a decided gain. The eye is pleased with the proportions, the horse is eased, and upon hard roads the difference of track is of no consequence. On the other hand, in the country roads, the well-worn ruts make the running of the carriage uneasy, whilst in town the driver often forgets that the curbstones will strike his hind wheels sooner than his front ones, and also more mud is thrown upon the panels. Under these circumstances it is very probable that the French plan will not find universal favour. If carriages had always to move along perfectly smooth roads such as a tramway of wood, stone, or iron, the use of wheels in overcoming friction would be their sole utility, and their height would be of small consequence. But as carriages are drawn along roads with loose stones and uneven surfaces, wheels are further useful in mounting these obstacles, and it is plain that a high wheel does this more easily than a low wheel. To demonstrate this, let us suppose a shallow ditch or gulley of a foot wide and 2 inches deep, a wheel 2 feet high would sink into this and touch the bottom, but a wheel 3 feet high would only sink an inch, and a wheel 4 feet 6 inches high would only sink half an inch (the wheels are supposed to cross the above-mentioned gulley at right angles), on account of their greater diameters. Consequently, while the large wheel would have to be lifted by a force sufficient to raise it half an inch, a force will have to be applied to the smaller wheel to raise it 2 inches, and under more disadvantageous circumstances, because the spokes are in this case the levers, and we know that the longer the lever the more easily is the load raised. That the leverage power of a high wheel is very great is shown by the advantages gained by a large wheel in locomotives and bicycles.