There is an insect well known to entomologists, called the Mole-cricket, because its structure and many of its habits are strangely similar to those of the animal from which it derives its name. At the upper part of the illustration is seen a portion of the fore-foot of the Mole-cricket, and a better implement of excavation can hardly be imagined.
The reader will probably have noticed that in both these creatures the spade, if we may so call it, is not a mere flat plate, but is cleft into several points. It thus answers the purpose of a fork as well as a spade, the several points serving to break up the soil, and the flat palm to throw the earth aside.
This principle is carried out even more fully in the fore-paw of the African Ant-bear, or Aard-vark (Orycteropus Capensis), a figure of which is given in the illustration. This animal is a great excavator, living in burrows of such dimensions that the wild boar is in the habit of making its home in them after they are deserted.
Something more, however, than a digging apparatus is needed for the Ant-bear. This animal feeds almost wholly on the Termites, which it obtains by tearing down the walls of their dwellings. Now, as these wonderful buildings are nearly as hard as brick, and, indeed, are composed of the same materials, it is necessary that the claws of the Ant-bear should be modified so as to be able to break through the walls. Accordingly, they are much more curved than those of the Mole and the Mole-cricket, and so serve for tearing as well as digging, being struck into the wall, and thus pulling it down, just as a labourer breaks down a bank with his mattock.
Indeed, had we wished to extend these analogies still further, we might easily have given the claws of the Aard-vark as a prototype of our English mattock. The same weapons as possessed by the Ant-bear of tropical America are used in exactly the same manner, but are even stronger, and extend to such a length that when the animal walks, it cannot stretch its claws out in front, but is obliged to double them under its feet.
Shears and Scissors.
These instruments are sure signs of civilisation, no savage nations having the least idea of them. Even the Kafir and Esquimaux tribes, which are such admirable workers in skin, never use scissors in shaping their garments, but invariably employ knives for that purpose. The Chinese, however, seem to have known scissors from time immemorial, and to have shaped them almost exactly like our own instruments. I possess one pair of tailor’s shears from China in which there is only one ring, namely, that for the thumb. The place of the other ring is taken by an elongated, slightly curved and moderately pointed rod of steel, which is used for tracing the pattern on the material preparatory to cutting it.
Simple as the scissors may seem, they combine several very important principles, namely, the inclined plane, the lever, and the cutting edge. Were they to be merely two edges moving directly upon each other, their effect would be comparatively slight; but, owing to the manner in which the blades are fixed at one end, they are drawn as it were over the object between them, and so divide it with comparative ease. In some instruments, such as the pruning scissors, there is only one cutting blade, the other being used merely as a support for the branch which is being cut.
A well-known example of a single cutting blade is found in the guillotine. In the earliest times of this invention an ordinary axe-head was suspended above the neck of the criminal. It was found, however, that its operation was very uncertain, simply because the blow was a direct one, and not oblique. The blade was then set obliquely, as in the present machine, and its effect was absolutely certain.
Perhaps some of my readers may be swordsmen, and therefore know the power of the “drawing cut,” by which a great effect may be produced with very little apparent exertion. Even in the simple operation of cutting bread we always use the knife diagonally, though perhaps we may be ignorant of the principle of the inclined plane.