Nature's Teachings

Then, exactly as the joints of a machine become stiff from non-usage, so do those of a human being. We will take, for example, the Indian Fakirs who vow that they will not move some limb from a definite posture. At first the exertion is trying and painful, but by degrees the disused joints lose their faculty of motion, and, even if their owner wished to move a limb, he could not do it.

The right-hand figure of the illustration represents the lubrication of an ordinary sewing machine, and the left-hand figure is a section of the human knee-joint, showing the gland which supplies the synovia.

Perhaps some of my readers may think that such a subject as the “Lazy-tongs” is too trivial for a work which deals, however lightly, with science. But there may be some who know the inestimable benefit of Lazy-tongs under certain conditions.

There are many cases where a severe injury has occurred, or where rheumatism has fixed its tiger-claws in the joints, so that movement is all but impossible. There may be no one in the room to help the invalid, and even to stretch the arm over the table is as impossible as to jump over the house.

Then it is that the real value of the Lazy-tongs becomes manifested, and that it shows itself in the light of a supplementary limb. With a mere movement of the fingers it can be stretched across any table which is likely to be placed before an invalid, and seize the required object by the tongs at the further end.

The only drawback to its use is, that the instrument cannot be shortened without opening the tongs. But, if some plan could be devised whereby the tongs could retain their hold under those conditions, the instrument would be a perfect one.

Exactly such a Lazy-tongs we have in Nature, in the well-known “mask of the larva and pupa of the Dragon-fly.” It is called a mask because, when closed, it covers the face.

It chiefly consists of two flat, horny plates, hinged in each other like a carpenter’s two-foot rule, and being capable of extension to a considerable length. The end is widened, and furnished with two jaws, which take the part of the tongs in the instrument above described.

This curious apparatus is used for the purpose of securing prey.

I have kept many of these creatures, and watched their mode of feeding. As has already been mentioned, they have two modes of progression, i.e. walking by means of legs like those of ordinary insects; and driving themselves along by ejecting water from the tail, on the principle of the rocket. As far as I have seen, the latter mode is always used in taking prey. The Dragon-fly larva always lives at the bottom of the water, though it can force itself to the surface if needful. And, like the dreaded ground-shark, it seizes its prey from beneath.

Its favourite food is the larva of the whirlwig-beetle, a fat white grub, with a number of white, soft, feathery gills fringing its sides. In order to produce a current of air over these gills, the larva wriggles itself up to a height of several inches, and then sinks slowly down, with the white gills floating on either side.

Should a Dragon-fly larva be near, it sees the grub ascending, glides quietly under it without using its legs so as to cause alarm, waits for it to sink, darts out the mask, seizes it in the jaws, drags it to its mouth, and the grub is seen no more. So voracious are these larvæ, that, if only two are kept in the same vessel, one is sure to devour the other.

Another good example of the Lazy-tongs is the Proboscis of the common House-fly. We have all seen these insects alight near sugar, or any other tempting food, unfold the proboscis, pour a drop of liquid in the sugar, dissolve it, suck it up, and then shut up the proboscis as if by hinges.

Another labour-saving machine is the Apple-parer, a comparatively modern invention. The principle is, that a knife is pressed lightly by a spring against a revolving apple, and set at such an angle that nothing but the outside peel can be removed. Where large numbers of apples have to be pared, as in making preserves or in hotels, this is a most useful invention.

When I first saw it at work, the operation seemed familiar to me, but I could not at first remember the parallel. At last it flashed across me that a Squirrel eating a nut was the natural parallel of the Paring Machine.

After splitting the shell and extracting the kernel, the Squirrel takes the latter between its fore-paws, presses it against its upper incisor teeth, and makes it revolve rapidly. In a second or two the kernel is perfectly peeled, and is then eaten.

In this case the incisor teeth of the Squirrel take the part of the knife, the muscles of the leg that of the spring, and the sharp edges of the upper teeth that of the knife. The structure of the Rodent teeth has already been explained in page 233.

The wonderful effects of water in breaking up the hardest rock have already been described. We will now proceed to another branch of the same subject.

Perhaps some of my readers may have wandered along our rocky coasts, and have seen how large masses of rock are continually detaching themselves, though they are so hard that a cold chisel is needed to make any impression upon them.

Then they fall into the sea, and are rolled backwards and forwards until they become smoothed and rounded, and are called pebbles, while the portion that is rubbed off them is called sand. The phenomenon is well shown in the wonderful Pebble Ridge of North Devon.

The real agent is ice.

We all know that, when water freezes, it expands considerably. This accounts for two phenomena.

First, as it expands, it becomes lighter than water, and consequently floats on the surface.

Next, there are few of us who have not seen water-bottles cracked by the freezing of the water. The most common, and perhaps the most unpleasant, example of this propensity is the bursting of water-pipes in the winter, followed by a flooding of the house when the thaw comes.

This is caused by the expansion of the frozen water, which will burst not only a thin leaden tube, but a stout iron vessel. Care should therefore be taken, at the beginning of winter, to cover up all exposed portions of leaden pipes, and there will then be no danger. There was one pipe in my house that was always bursting, but after I covered it with two or three layers of carpet placed loosely over each other, so as to entangle the air and form a non-conductor, the pipe has never frozen, and the water supply has been uninterrupted by the severest frosts.

I am told that a still better plan exists, especially in places where the pipes cannot be thoroughly protected by external wrappings. Let six inches or so of the leaden pipe be removed, and its place supplied by a vulcanised india-rubber tube.

The ice must expand somewhere, and chooses the spot where least resistance is offered to it. Consequently, it expands in the india-rubber tube, but does not break it, and, when the thaw comes, there is no overflow of water.

Man utilises this power of ice in stone-splitting. Instead of taking the trouble to cut the stone by manual labour, the workmen bore a series of holes, fill them with water, insert tightly a wooden plug to prevent the ice, when formed, from oozing out of the holes, and leave the rest for the frost to do.

A like effect is produced in the warm weather by substituting similar plugs, but quite dry, having been baked for hours in an oven, for the purpose of driving out every particle of moisture. These plugs are hammered into the holes as deeply as they will go, and there left. Even if there be no rain, the nightly dews make their way into the pores of the dry wood, and cause it to swell with such irresistible force that the stone is split with scarcely any manual labour on the part of the workmen.

Yet another plan for cutting hard stones. Some of my readers may be aware that a singularly ingenious instrument has been invented for cutting boles in granite and other hard rocks. It is called the Diamond Drill, because its tip is armed with uncut diamonds.

It is necessary that the diamond should not be cut, as the natural edges are needed. A glazier’s diamond, for example, is always set as it came out of the mine. The stories that are told about cutting out panes of glass with a diamond ring are all absurd. A diamond, when it has once passed through the hands of the jeweller, cannot cut glass. It can scratch glass, but not one whit better than a flake of ordinary flint.

It is found that the Diamond Drill works with wondrous rapidity, cutting away the stone with ease, and suffering scarcely any damage itself. The tube to the end of which the diamonds are fixed is generally made in telescopic fashion, so as to allow it to penetrate deeply into the rock, without the necessity of shifting the machine by which it is turned. I need hardly say that its rate of speed is very great indeed.

Our old friend, the Gad-fly, again affords an example of a parallel.

The ovipositor is tubular, telescopic, and furnished at the top with five little hard, sharp, scaly knobs, which act the same part as the diamonds of the mining tool. Even the scoop-like shape of the tip, and the telescopic shaft, are almost identical in both instances.

CHAPTER XIII.
TELESCOPIC TUBES.—DIRECT ACTION.—DISTRIBUTION OF WEIGHT.—TREE-CLIMBING.—THE WHEEL

Telescopic Tubes, their Structure and Uses.—The Japanese Fishing-rod.—The Tripod Wheel-bearer and its Telescopic Structure.—The Rat-tailed Maggot.—Locomotion.—Direct Action.—The Rocket, the Water Tourniquet, and Electric Tourniquet.—Cuttle-fish.—The Flying Squids.—The Paper Nautilus.—Proceedings of newly-hatched Calamaries.—Larva of the Dragonfly.—Distribution of Weight.—The Snow-shoe, its Structure and Mode of using it.—The Skidor of Norway.—A formidable Rifle Corps.—The Mud-patten.—Foot of Duck tribe.—Foot of Jacana.—Locomotion of Water-gnat.—Tree-climbing.—Mode of ascending Palm-trees.—The Value of a Hoop.—The “Girt Pupa” and Butterfly.—Principle of the Wheel.—The primitive Wooden Wheel.—Spoked Wheels.—Driving Wheel of the Bicycle.—Naturally spoked Wheel of the Chirodota.

 

Means and Appliances (continued)

WE will now treat rather more in detail the two subjects which were lightly touched upon at the end of the last chapter.

The reader will remember that the diamond-headed borer is made in telescope form, so as to be adjustable at pleasure. It was also remarked that the ovipositor of the Gad-fly was made in a similar fashion, so as to be withdrawn within the body of the insect when not needed, and protrusible to a considerable extent when the Gad-fly wishes to deposit her eggs.

As to our modern telescopes and opera-glasses, they are so familiar that there is little use in describing them, except to say that their framework consists of a number of tubes of gradually lessening diameter, the one sliding within the other, so that the instrument can be lengthened or shortened at will, so as to suit the focus of the observing eye.

A very ingenious adaptation of the telescopic principle is seen in the Japanese fishing-rod, which is now tolerably well known. Our own telescopic rods require to be withdrawn at the butt-end, and then fitted together in front. But the Japanese rods are so made that, after taking off the ferrule of the seeming walking-stick, a mere fling of the hand will send joint after joint flying out, and fixing themselves in regular succession. So admirably are these rods made, that even blowing into the butt-end will have the same effect.

One of the most perfect, if not the most perfect, example of the telescopic tube is to be found in the Tripod Wheel-bearer (Actinurus), one of the numerous aquatic Rotifers.

It is not usually so small as the generality of its class, being nearly one-twentieth of an inch in length, and visible to the unassisted eye, provided that the owner of the eye in question knows how to use it.

When placed under a microscope of moderate power, the Actinurus is seen to be built almost wholly upon the telescopic pattern. Only the centre of the body remains stationary, the two ends being framed on the principle of the telescopic tube, and capable of being enclosed within the central portion, just as is the case with the Japanese fishing-rod.

In the illustration the Actinurus is shown in two attitudes. In the upper figure it is represented as having the fore-part of the body entirely, and the tail part nearly, withdrawn within the central portion. The lower figure shows the same specimen with all its telescopic tubes drawn out to full length.

The creature is perpetually elongating and contracting its body by means of these tubes, so that a measurement of its length is not easy to obtain.

A full and interesting description of this curious Rotifer may be found in Gosse’s “Evenings at the Microscope,” p. 300. The long tails of the Rat-tailed Maggot, already described under the head of Diving, are good examples of the drawtube as found in Nature.

Locomotion.—Direct Action

The second point which has to be elucidated is that or progress by means of Direct Action.

We have already seen how vessels can be propelled by sail, oar, paddle, or screw. We have now to consider a mode of progress which requires none of these things, but which works by means of Direct Action.

Such, for example, is the progress of a Rocket through the air.

The heated gases rush out with tremendous violence, and, by their pressure, urge the heavy rocket into the air with the rush, roar, and bang so familiar to all who have witnessed a good display of fireworks.

A rocket in the act of ascent is shown in the uppermost figure of the accompanying illustration.

Below it is shown the Water Turbine, the principle of which is evident from the sketch.

From each of the apertures a stream of water is forcibly directed, and, by its resistance, spins the vessel round and round. There are several shops in London in which this instrument may be seen at work.

Although in such positions it is necessarily a mere toy, it carries with it, in common with many other toys, the germs of valuable inventions. Indeed, there have been attempts to utilise the principle of Direct Action in the propulsion of vessels, but as yet the mechanical difficulties have proved practically insuperable, and, although a vessel has been thus propelled, the expense has been heavier than that of the paddle or screw, and the speed not nearly so great.

On the right hand of the illustration is another example of Direct Action, called the Electric Tourniquet.

In the two previously mentioned instruments the motive power is visible, but in this it is invisible except in the dark.

The principle is exactly the same as in the pocket or water tourniquet; but, instead of heated air or a stream of water, electricity is used. The instrument is attached to an electric machine, and fully charged. The electric fluid rushes out of the points, forces itself against the air, and so, by its recoil, drives the machine round and round upon its pivot.

We will now take two examples of Direct Action as found in Nature.

Perhaps many of my readers have seen the Octopus, and admired the manner in which it glides through the water, trailing its long arms behind it. Whence the force comes is not easily seen, and the creature appears to move almost by volition. In reality, however, it employs Direct Action. It takes water into the body, and then it ejects it through a tube called the “siphon” with such force that the animal is propelled backwards through the water.

Some of the creatures belonging to the Cuttles, and popularly called Squids, can use such extraordinary powers that they can project themselves far out of the water. In consequence of this power, they are sometimes called Flying Squids, and, as they have been known to shoot themselves completely over the hull of a large ship, they well deserve the name.

The common Squid of our coasts, which furnishes the so-called Cuttle-bone, affords us a good example of Direct Action. I once hatched a number of young Squids from the grape-like eggs, and it was most curious to see how the little creatures shot about as soon as they escaped from the egg.

They also utilised the siphon in another way. Poising themselves just above the sand with which the bottom of the vessel was covered, they directed a stream of water upon it, and thus formed little cavities into which they settled like birds into their nests.

The figure represents the Paper Nautilus as it appears while passing through the water. Just at the base of the tentacles is seen the short siphon, from which it is pouring the stream of water which drives it along.

Below the Nautilus is seen the larva of the common Dragonfly. We have, when treating of the Lazy-tongs, already described the mode in which the insect takes its prey, and our object could not be served by repetition. Suffice it to say that the insect is shown in the act of ejecting water, and so shooting itself along in preparation for seizing prey.

Distribution of Weight

Being on the subject of locomotion, we will examine a few of the contrivances by which a man is enabled to pass in safety over soft substances into which he would otherwise sink.

The first and best-known of these is the Snow-shoe of Northern America. It is a framework of wood, shaped as shown in the upper figure on the right-hand side, and strengthened by two cross-bars. The interior of the “shoe” is filled in with hide thongs arranged much like those of a racket, and stretched as tightly. The front of the snow-shoe is slightly turned up, so as to avoid the danger of the point sticking in the snow, an event which, however, generally happens to a novice.

These instruments are of considerable size, a specimen in my collection measuring exactly five feet in length, by fifteen inches in width.

Supported on the snow-shoe, the hunter is enabled to glide unhurt over the deep snow in which he must have sunk without some such aid. He can thus hunt the bison, the wapiti, or any of the larger animals, being able to pass rapidly over the surface, while they are laboriously ploughing their way through the snow-drifts.

It occasionally happens that the snow falls before the shoes are ready. In this case the hunter is obliged to extemporise snow-shoes by cutting them out of thin boards.

Several years ago, when snow fell heavily and remained unmelted for many days, some Canadians, who were visiting England, made quite a sensation by donning their snow-shoes, and travelling over the snow-clad country. It was very pretty to see the easy way in which they could shoot down a hill, and to watch the peculiar gait which is needed by the snow-shoe.

At the bottom of the illustration is shown a portion of a curious skate used in Norway, and called Skidor.

These remarkable implements achieve by means of length the task which the snow-shoe accomplishes by width. They are made of wood, and, though but a few inches in width, are ten feet or more in length. One is always a few feet shorter than the other, for the convenience of turning. Much practice is needed for the management of the Skidors, but, when they are fairly mastered, they enable their owner to travel at a wonderful pace.

The Norwegian hunter is quite as dependent on his Skidor as the North American on his Snow-shoe, and uses it for exactly the same purpose. A corps of these hunters has been organized for war, and very formidable they were, hanging on the skirts of the enemy, and giving him no rest, day or night. They never came within fifty yards of each other, so that even cannon were useless; and, as soon as they thought that they were endangered, they dispersed in all directions, only to reunite and swoop down again on the enemy at the first opportunity.

The central figure represents the Mud-patten, which, as its name implies, plays the same part towards mud that the snow-shoe and skidor do to the snow. Like them, also, it is not easy to manage; and a novice is tolerably certain to drive the front of the patten into the mud, and so get an awkward and not aromatic fall.

This patten, which is merely a square piece of board attached to the foot, is in use on many of our coasts where the ebbing tide runs out to a great distance, leaving a vast expanse of soft mud. Like the skidor and the snow-shoe, it is mostly used by sportsmen, especially in the winter, when wild-duck shooting sets in.

Aided by the pattens, a sportsman can travel for miles over mud that would otherwise swallow him up, shoot his birds, and secure them when fallen. While engaged in winter shooting on the Medway, we have often lost birds because they fell beyond a deep mud-bank, and we had no means of crossing it.

On the left hand of the illustration are some natural parallels of these artificial aids. The two upper figures represent two forms of webbed feet, and the analogy between them and the snow-shoe and mud-patten is too obvious to need explanation.

In the centre is the foot of the Jacana, an Asiatic bird. Its foot may well be taken as the analogue of the skidor, length taking the place of breadth, and enabling the weight to be distributed over a large surface.

This bird finds its food in rivers and lakes, and, by reason of its enormously long toes, can walk with safety over slight floating vegetation, which would give way at once under the tread of any bird except a Jacana. Very good representations of this bird are to be seen in Japanese works of art, especially those which are mounted as screens. Even the peculiar gait of the bird is given with marvellous truth.

The last figure represents the common Water-gnat (Gerris), which may be seen in almost any piece of fresh water, however small. Ponds that are open to the south, and sheltered from the north wind, are its favourite localities.

It is a carnivorous being, feeding almost wholly on insects that fall into the water. In order to capture them, it runs rapidly over the surface of the water, the long slender legs distributing its weight over a large surface, and so keeping it from sinking. Only the last two pairs of legs are employed for this purpose, the first pair being held in front of the body, and used for the purpose of capturing prey.

Tree-climbing

Another curious aid to locomotion is shown in the accompanying illustration.

In many parts of the world, where the cocoa-nut palm grows, the natives have invented a simple, but ingenious, plan for ascending the tall, curved stem. Such a thing as an upright palm-tree is unknown, and consequently the ascent of the branchless stem is not an easy task without artificial assistance.

When I treated of Warfare and the different modes of scaling walls, the climbing-spur was casually mentioned. The implement of the palm-climber, however, is simpler and more effective, as it leaves both hands at liberty when desired.

The man cuts a long piece of one of the tough and almost unbreakable creepers which festoon the trees of tropical climes. He passes it round the trunk which he wishes to climb, and fastens the ends firmly together, so as to form a large loose hoop. He then passes the hoop over his head, until it presses against his back, as seen in the illustration, and serves to support him as he leans against it.

Taking the hoop by the two sides, he lifts it up the trunk as far as he can, places the soles of his feet against the tree, and so walks up it, hitching the hoop upwards at every step. When he has reached the top of the tree, he supports himself entirely by the hoop, while his hands are at liberty to be used in getting the cocoa-nuts.

In the insect world there are many examples of support being given by a belt passing round the body.

Among the Butterflies, for example, there are many which, in their pupal stage of existence, are attached to upright stems. They are fixed to the stem by a few threads at the tail, answering to the feet of the tree-climber, while the body is kept in position by a stout silken thread passed loosely round it.

The illustration represents the pupa of the common Swallow-tailed Butterfly, while in the centre is the same insect in the perfect state as it appears when resting. It really seems as if the ancient habit of the pupa had been remembered by the perfect insect, the long ends of the hinder wings taking the place of the pupal tail, and the legs that of the belt.

The Wheel

Yet another aid to locomotion is found in the Wheel, a contrivance for diminishing friction.

When man first learnt that heavier weights could be dragged than carried, he simply placed them on flat boards to which ropes were attached. The next step was necessarily the invention of the sledge, the burden resting on two parallel runners, the ends of which were slightly curved so as to prevent them from hitching against any small obstruction. In some countries—such, for example, as in Esquimaux-land—the sledge is the only vehicle practicable, and even Europeans, when they visit that country, are fain to adopt the sledge if they would live.

But, in more temperate zones, the Wheel is paramount. In its earlier stages the wheel was a very simple business. It was simply a section of, a tree-trunk, dubbed roughly round, and with a hole in the centre, through which the axle passed. Such wheels are still in existence in many parts of Europe; and, owing to the want of regularity of outline in the circumference, and the utter absence of grease, the wheels keep up a continuous shriek, almost deafening to those who are unused to it, but perfectly unheeded by those who own or drive the vehicle.

The next improvement was to make the circumference of the wheel as perfectly circular as the art of man could devise, and, instead of having the wheel solid, to fill up its interior with spokes, thus gaining lightness and strength at the same time.

Of all locomotive wheels, I suppose that the modern Bicycle affords the best example. The driving wheel is larger than the hind wheel of an ordinary coach, and yet the spokes are not nearly so thick as the porcupine quill with which this account is written.

If we look at the ancient sculptures and paintings of Egypt and Assyria, as preserved in the British Museum, we shall see that either kind of wheel was used according to the work which it had to do. The solid, uneven, squeaking, wooden wheel was devoted to agriculture, while the light, spoked wheel was sacred either to warfare or hunting.

Let us hope that in the two latter cases some modicum of grease might have been used, as the outcries of tortured and unlubricated machinery are enough to drive away all wild beasts which come within the range of its complaints, while the nervous system of hunter or warrior must have been seriously damaged by it.

Even in such a structure as the spoked Wheel, Nature has anticipated Man.

My readers may remember that, when treating of nautical matters, I mentioned the singular anchor-shaped spicules that are found upon one of the sea-slugs, called Synapta.

There is another group of these creatures inhabiting the Mediterranean, in which the skin-spicules take a different form. Like those of the Synapta, they are too small and translucent to be seen without the aid of the microscope and carefully adjusted light. But, just as the spicules of the Synapta resemble the ancient anchor, so do those of the Chirodota resemble the ancient wheel, the similitude being in both cases absolutely startling.

Not only that, but, as all readers must be aware, if they have studied practical mechanics, there are many machines which are toothed on the inner, and not the outer, side of the circumference. Here, in the Chirodota, the inner toothing is manifest.

What purpose it serves we know not. The Chirodota’s wheels (of which there are thousands) never revolve, neither do the anchors of the Synapta hold the ground. Yet the very fact that such exceedingly minute objects should be so carefully constructed tells us at once that they must have some important purpose to serve, though at present that purpose is a mystery which no one has attempted to solve.

I have little doubt that when the hour and the man arrive, as arrive they surely will, we shall find in these tiny and almost unrecognised spicules the keys to treasures of wisdom which at present have been opened to no human being.

The whole history of the progress of the human race shows that facts have been allowed to accumulate, fought about, and turned in all directions, before the generaliser comes who pierces to the heart of everything, reduces apparent discrepancies to harmony, and usually is rewarded by finding some one else assume the credit of his discoveries, and receive all the honours and emoluments.