It is also true that a slight hollow will exist under the ball of a well-arched foot, even when pressed upon by the weight of the body. This may be filled up if desired, for, being so small, it is a matter of indifference whether it is so or not, while there is perfect safety in letting it alone. We see, then, that while one characteristic of the Plumer boot—the long heel—is a very valuable one, another—that of filling under the transverse arch—is useless, or positively injurious. The first, or good quality, however, overbalances the latter, and therefore the boot is an improvement upon the old or common style. The true and natural-shaped boot would have a _flat_ or _level_ surface from heel to toe on the sole, not wholly, _but precisely where in this it is hollowed out_. The parts on each side of the level strip would be slightly convex, like the corresponding parts of the foot; not too much so, however, for then the last would be too rounding on the bottom, taking the whole width in view, which is as bad a fault as the hollow, or even worse; as it interferes more with the spreading of the transverse arch, and, by making a _concave_ upper surface to the insole of the shoe, compels the ball to tread into just such a hollow as would fit a broken-down, splay foot. The natural inference is that such a shoe would tend to favour the production of just such a foot. It is believed that the broken-down transverse arch will almost always be found accompanied by the broken-down arch of the instep. Though the latter may exist without the former, yet we suspect that the two incline to go together—that the sinking of the greater arch tends to carry down the other along with it, while a natural weakness of muscle would be a predisposing condition. If there are other causes they are not yet known. The last supposition being correct, then the most direct way to a cure would be to restore the arch of the _instep_ to its proper shape and position; which would probably have the same tendency to raise the other, that its depression had to break it down. The grand recipe for this, as already given, is the long heel; which can be made upon any kind of covering, whatever its peculiarities. The use of the muscles of the toes must also come in as an auxiliary help not to be underrated.