The Cassava Press and its Structure.—Mode of using it.—The Siamese Link.—An ingenious Robbery.—Muscles and their Mode of Action.—Human Arms and Steelyard.—Change of Direction.—The Human Hand and Wrist.—Story of a Carpenter.—The Pulley.—Reduction by Friction.—Past and present Engines.—Oiling Machines.—Treatment of the Sewing Machine.—Use of Paraffine.—Disuse of Machine hurtful.—Human Joints.—Synovia and its Value.—Disuse of Joints hurtful.—The Lazy-tongs and its Usefulness to Invalids.—Suggestions for Improvement.—Larva of the Dragonfly and its Mask.—Curious Mode of seizing Prey.—Proboscis of the Housefly, and Mode of using it.—The Apple-parer.—Squirrel and Nut.—Structure of Teeth.—Rock-splitting.—Powers of Ice.—How the Pebble-ridge is formed.—Splitting Stones by Moisture.—The Diamond Drill.—Ovipositor of the Gad-fly.—Curious Similitude of Structure.
The Cassava Press and its Structure.—Mode of using it.—The Siamese Link.—An ingenious Robbery.—Muscles and their Mode of Action.—Human Arms and Steelyard.—Change of Direction.—The Human Hand and Wrist.—Story of a Carpenter.—The Pulley.—Reduction by Friction.—Past and present Engines.—Oiling Machines.—Treatment of the Sewing Machine.—Use of Paraffine.—Disuse of Machine hurtful.—Human Joints.—Synovia and its Value.—Disuse of Joints hurtful.—The Lazy-tongs and its Usefulness to Invalids.—Suggestions for Improvement.—Larva of the Dragonfly and its Mask.—Curious Mode of seizing Prey.—Proboscis of the Housefly, and Mode of using it.—The Apple-parer.—Squirrel and Nut.—Structure of Teeth.—Rock-splitting.—Powers of Ice.—How the Pebble-ridge is formed.—Splitting Stones by Moisture.—The Diamond Drill.—Ovipositor of the Gad-fly.—Curious Similitude of Structure.
IN this chapter we will take some miscellaneous appliances of force both in Art and Nature.
In the accompanying illustration is shown the Cassava Press of Southern America, a most effective and simple instrument for extracting the juices of the root. These juices are poisonous when raw, but, when properly boiled and cooked, they make an excellent sauce.
The press in question is an elastic tube made of flat strips of cane woven together exactly like the “Siamese Link,” which will be presently described. The cassava root, after having been scraped until it resembles horseradish, is forced into the press until it can hold no more. The result is, that the tube is shortened and thickened, being widest in the middle.
It is then hung by its upper loop to the horizontal beam of a hut. A long pole is passed through the lower loop, the short end is placed under a projecting peg on the upright post of the house, and a heavy weight attached to the longer end. A powerful leverage is thus obtained, the tube is forcibly shortened,and the juice exudes through the apertures of the woven cane.
Image unavailable: CASSAVA PRESS.CASSAVA PRESS.
When it begins to run slowly, a woman seats herself at the end of the pole, so as to increase its weight. I must mention here that in the illustration the press is too near the middle of the pole. This is because the exigences of our page do not admit of the requisite length. But if the reader will kindly assume the end to which the stone is attached to be three or four times longer, he will have an idea of the great power which is exerted upon the cassava.
On the left hand of the illustration is the same cassava press as seen when empty, and both figures, as well as that of the pot for receiving the juice, are taken from specimens in my collection.
Onthe right hand of the following illustration is the Siamese Link, which caused such a sensation when it first came out.
A finger is inserted at each end, and, when the owner attempts to withdraw them, the Link contracts, and the harder the pull, the tighter is the hold. If the fourth instead of the first finger be employed, the hold of the Link is exceedingly strong.
The only mode of release is by pushing the fingers together, when the Link will relax. It should then be held by theremaining fingers of one hand, so that it shall not contract again, and the finger of the other hand comes out at once.
An ingenious robbery was once committed by means of the Siamese Link. A man of good address struck up an acquaintance with a jeweller. One day he produced a Siamese Link, and challenged him to get his fingers out when once they were in. So the jeweller was told to put his hands behind his back, and push his little fingers as far in as he could.
Image unavailable: MUSCLES Of LEG. SIAMESE LINK.MUSCLES Of LEG. SIAMESE LINK.
This he did, when the treacherous friend made a clean sweep of all the rings, brooches, ear-rings, and such jewellery as was within his reach, while the unfortunate jeweller was vainly tugging at the Link. This only occupied a few seconds for a practised hand, and the thief quietly opened the door, shut it, and was lost in the passing crowd before the jeweller could recover from his surprise.
Onthe left of the same illustration is a view of the muscles of the human leg, which, as the reader will see, are curiously like the distended cassava press. Although the mode of applying the force differs, the principle is the same.
In the latter case an external force is applied to the press, but in the latter an internal, or rather a central, force isapplied to the bones. It is evident that if a similar process were carried on with the cassava press, and the central portion forcibly distended, the supports at either end would be drawn powerfully towards each other. Substitute the muscle for the press, and the bones for the poles, and this is muscular action.
Herewe have a diagram which speaks for itself, as far as muscular action is concerned, but there is another point to which we shall presently pass.
Image unavailable: HUMAN ARM. STEELYARD.HUMAN ARM. STEELYARD.
The muscle of the arm is seen running along the bone, passing over the elbow, where it is held down by a tendinous band, and, by its contraction, enabling the arm to be bent so as to uphold a considerable weight. The mechanical analogy between this arrangement and the common Steelyard is too evident to need any explanation except inspection of the diagram.
Thereis, however, another point which is worthy of consideration. The muscle does not proceed at once from the shoulder to the wrist, but passes under the tendinous band above mentioned, and so produces a change of direction when the arm is bent.
There is a more complicated arrangement of a similar character in the human hand, a diagram of which is given in the left-hand figure of the accompanying illustration.
The fingers are, of course, moved by a set of tendons, and the muscles, from which these tendons spring, are attached to the fore-arm (I purposely omit the scientific titles, though they would be much easier to write). Any of my readers can prove this for themselves.
Let him first grasp the upper arm firmly, and bend the limbs, and he will at once find that the swelling of the muscle shows the source of power.
Then let him do the same, but grasp the fore-arm, and he will find that the muscles are quiescent, showing that the former set of muscles belong to the entire arm, and not to the fingers, while the muscles of the lower arm have nothing to do with the bending of that limb.
Now let him grasp the fore-arm, and open and close the fingers, and he will feel a whole set of muscles rise, and swell and harden under his grasp. Next let him bend his hand inwards, and he will find that the fingers work perfectly well, though the direction of force is changed.
This is owing to a band of tendons passing across the wrist, under which the finger-tendons play. The course of the tendons is marked in the illustration by leaving them white.
The wondrous structure of the human hand and its multitudinous tendons can only be appreciated by actual dissection, but an idea of their variety and use may be obtained by watching the hands of a skilful pianoforte-player. This struck me forcibly the first time that I ever heard Thalberg play.
While on the subject of tendons, I may mention a curious case. A journeyman carpenter missed a blow with his axe, and struck his left hand at the junction of the thumb and wrist. The important tendon was severed, and the inner muscles, having no counteracting force, dragged the thumb into the hollow of the hand.
To all appearance, the man could no longer earn a living as a carpenter. But he would not be discouraged, and while he was in hospital he borrowed a book, and studied the anatomy of the human hand. By means of this knowledge he constructed a sort of semi-glove, in which he introduced pieces of watch-spring, that supplied the place of the lost tendon.
Not content with this, he studied Euclid for the purposes of his trade, so as to get the most possible out of a piece of wood of given dimensions, and be able to go straight to his mark by a problem, instead of doing it slowly and clumsily with a two-foot rule and a pair of compasses. When I saw him last he was a master carpenter in a large and increasing business.
Man has unconsciously imitated Nature in the invention of the Pulley, whereby the direction of force may be altered almost at will. In this case the cord takes the part of the working tendon, and the Pulley of the fixed tendinous crossbar. There is much matter of interest in the tendons, but, as our space is fast waning, I must resist the temptation of describing them.
Inall machinery one of the chief objects of the machinist is to reduce friction as much as possible. He makes all the joints as smooth as tools can polish, and always introduces oil or some lubricating substance into the joints. Otherwise the engine rattles with a noise proportionate to its power, and wastes its force on the friction.
Image unavailable: TENDONS OF HAND. PULLEY.TENDONS OF HAND. PULLEY.
In my childish days a steam-engine of any kind used to rattle so loudly that conversation was almost impossible. Now they are made with such perfection, that the vast engines in use at the pumping stations of the metropolitan drainage are almost absolutely silent.
There is the enormous hall, filled with gigantic beams and rods, and cranks, and wheels. A single man turns a little handle, and the whole machinery starts into life. Beams rock, cranks and wheels revolve, rods slide up and down, and all in a silence which is nearly appalling in its manifestation of unassuming strength. Indeed, many a hand sewing machinemakes far more noise than one of those giant engines, and all because in the latter friction is avoided as far as possible, every screw is well braced up, and every joint is kept well lubricated.
Here I may observe that few sewing machines get fair play. They rattle, they squeak, they become stiffer daily, they snap the thread, and then decline work altogether. And in almost every case this is done by neglect on the part of the owner, who does not lubricate every point of the machine which works upon another.
Image unavailable: LUBRICATION OF JOINT. OILING MACHINE.LUBRICATION OF JOINT. OILING MACHINE.
Ladies especially are very careless in this respect, and will mostly omit three or four of the oiling points. They might just as well omit them all, as a single unoiled point will disarrange the harmonious motion of the whole machine. I have often been called in as surgeon in such cases, and have almost invariably been able to point to several spots which needed oil, and did not get it. Sometimes, out of false economy, an inferior oil is used, which speedily clogs and hardens, and stops all movement. In such a case the best remedy is to apply paraffine liberally, and use it for a quarter of an hour or so. It will soon dissolve the clogged oil, which may be worked out by turning the handle or crank of the machine.
Of course the best remedy is to take the machine to pieces, polish the joints, lubricate them, and put it together again. But this is a perilous process, and an amateur, if he tries it, will generally find himself with half-a-dozen pieces for which he can find no place. Paraffine will answer every purpose, and I have released many a stiffened machine by its use.
Then some people leave their machines untouched for days, or even weeks, and then wonder that they work stiffly. Every day the machine should he worked, if only for a few seconds, and then it will seldom stiffen. It is just the same with steamers. When they are in harbour, though the fires be out, and they are not meant to move for weeks, the engines are always turned round at least once daily.
Boththese rules hold good in the animal kingdom.
To every joint there are attached certain glands that supply a kind of oily substance technically named “synovia,” which acts exactly the same part as the oil or grease of machinery. If these glands do not do their duty, and the supply of synovia be defective, the joints become stiff, painful, and crackle when they are moved.
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.
Perhapssome 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 beforean 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.
Exactlysuch 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.
Image unavailable: HEAD AND PROBOSCIS OF HOUSE-FLY. MASK OF DRAGON-FLY LARVA. LAZY-TONGS.HEAD AND PROBOSCIS OF HOUSE-FLY. MASK OF DRAGON-FLY LARVA. LAZY-TONGS.
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 severalinches, 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.
Anothergood 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.
Anotherlabour-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.
Image unavailable: SQUIRREL AND NUT. APPLE PARER.SQUIRREL AND NUT. APPLE PARER.
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, theSquirrel 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.
Thewonderful effects of water in breaking up the hardest rock have already been described. We will now proceed to another branch of the same subject.
Image unavailable: FROST-CLEFT ROCK. STONE-SPLITTING.FROST-CLEFT ROCK. STONE-SPLITTING.
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-bottlescracked 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 icemustexpand 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.
Manutilises 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.
Yetanother plan for cutting hard stones. Some of my readers may be aware that a singularly ingenious instrumenthas 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.
Image unavailable: BORER OF ŒSTRUS. DIAMOND-HEADED BORER.BORER OF ŒSTRUS. DIAMOND-HEADED BORER.
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.
Ourold 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.
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.
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.
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 wellknown. 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.
Oneof 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.
Image unavailable: ACTINURUS TAIL, OPEN AND CLOSED (MAGNIFIED). TELESCOPE.ACTINURUS TAIL, OPEN AND CLOSED (MAGNIFIED). TELESCOPE.
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.
Thesecond point which has to be elucidated is that or progress by means of Direct Action.
Image unavailable: NAUTILUS. LARVA OF DRAGON-FLY. ROCKET. WATER TOURNIQUET. ELECTRIC TOURNIQUET.NAUTILUS. LARVA OF DRAGON-FLY. ROCKET. WATER TOURNIQUET. ELECTRIC TOURNIQUET.
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.
Wewill 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 consequenceof 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.
Beingon 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.
Image unavailable: FEET OF DUCKS. SNOW-SHOE. FOOT OF JACANA. MUD-PATTEN. WATER-GNAT. SKIDOR.FEET OF DUCKS. SNOW-SHOE. FOOT OF JACANA. MUD-PATTEN. WATER-GNAT. SKIDOR.
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.
Atthe 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.
Thecentral 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.
Onthe left hand of the illustration are some natural parallelsof 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.
Anothercurious 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.
Image unavailable: GIRT PUPA AND BUTTERFLY. CLIMBING PALM-TREE.GIRT PUPA AND BUTTERFLY. CLIMBING PALM-TREE.
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.
Inthe 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 ifthe 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.
Yetanother aid to locomotion is found in theWheel, a contrivance for diminishing friction.
Image unavailable: WHEEL-SPICULE OF CHIBODOTA. CART-WHEEL.WHEEL-SPICULE OF CHIBODOTA. CART-WHEEL.
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.
Evenin 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, neitherdo 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.