TOOLS.
CHAPTER II.
THE SAW AND ITS VARIETIES.
Cutting Tools and their working.—Structure of the Edge.—The Kris.—Edge of a Razor.—The Sword and the Apple.—Australian Saw.—Fretwork Saw.—Various Saw-flies.—The Pioneer’s Saw.—Cutting Tools of Trichiosoma.—Side Teeth of the Saws.—The Cordon Saw, or Band Saw.—Tooth-ribbon of Whelks, Slugs, and other Molluscs.—The Dog-whelk, or Purpura.—The Circular Saw.—Sawyer-beetles and their Mode of Work.
STILL keeping to the Cutting Tools and their varieties, we come to the Saw, i.e. the cutting tool set with teeth upon its edge. Now, in plain fact, there is no cutting instrument that does not more or less partake of the character of the Saw; for, in the first place, it is absolutely impossible for man to grind an edge so fine that, when magnified, it will not appear to be deeply notched, and, in the next place, its cutting powers are greatly due to the notches and teeth, and the direction of their points.
We will take both these subjects in turn.
First, as to the notches, or serrated edge. I have now before me two instruments, each the best of their kind, and in both of which the serrations are essential to efficacy. The first is a Malayan dagger, or “kris,” and the second is a surgeon’s lancet, made by Ferguson, of London.
In the kris the edge is intentionally serrated, having been eaten away by means of acids until the required effect was produced. The Malayans know by experience that such an edge is most deadly in a weapon, and that it will cut certain vital parts which a smoother edge might pass without doing any damage.
Now we will take the lancet, and put it under the microscope, when it assumes the most curious resemblance to the kris. Its mirror-like surface looks as if it had been very roughly treated with a coarse file, while its thin and delicate edge, which is perfectly smooth to the eye, and which will pass through a piece of stretched wash-leather without any apparent opposition, becomes as rough and jagged as that of the Malayan weapon.
Take even, for example, the common butcher’s knife, which is perpetually being sharpened on the “steel” that hangs at his belt. The reader may observe that the butcher does not rub the blade of his knife backwards and forwards on the steel, as unskilful persons do. Rapid as is the movement gained by constant practice, any one may see that the blade is always moved in one direction, so as to force the microscopical teeth to point one way, and so to act as a saw when the knife is drawn across the meat.
The power of these teeth or notches may be inferred from a well-known fact. If a razor, no matter how sharp, be pressed upon the human skin without any “draw,” it will indent the skin, but not cut it, while the slightest drawing movement will cause a deep wound. It is the knowledge of this fact that enables an expert swordsman to sever an apple placed on the palm of the bare hand, without even scratching the skin. I have witnessed this feat, and at once saw that it was due to the absence of any “draw” to the cut. The apple was laid on the palm of the hand, which was opened as widely as possible, so as to flatten it. The sword was then brought down on the apple with a sort of chopping movement, so that, although it indented the skin, it did not even inflict a scratch.
By the use of the “drawing” movement, the same sword severed a gauze veil laid across it, the two halves floating in opposite directions. By the same cut, I have seen some astonishing feats performed with an Indian sword now in my collection, the objects of attack falling asunder as if by magic, without any apparent force being used.