Nature's Teachings. John George Wood

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      If the creature be removed from the tube, and carefully examined, a number of projections will be seen, in each of which is a perforation. If the animal be pressed, a slight glass-like bristle passes through the perforation, and can easily be removed. If properly treated, and placed under a high power of the microscope, the tiny bristle resolves itself into the remarkable object which is shown on the left hand of the illustration.

      It consists of a number of spear-like rods, each having a straight shaft, and a curved and pointed tip, deeply barbed on the inner portion of the curve. These curious bundles of spicules can be protruded or retracted at pleasure, and, as they are all directed backwards, it is evident that when they are pushed against the sides of the tube, either the points or the barbs must catch against the membrane which lines the tube, and so propel the animal upwards. When it wishes to descend, it uses another set of implements, and withdraws the first within their sheaths.

      This is exactly analogous to the mode of progression employed by punters, who, after they have placed the pole against the bed of the stream, and run along the punt so as to push it as fast as possible, immediately withdraw the pole, and take it to the head of the punt, ready for another push. This, as the reader will see, is exactly the plan pursued by the Serpula in lengthening itself when it wishes to advance, and so to press its spicules against the sides of its tube, and in shortening itself and withdrawing the spicules ready for another push.

      Another needful accessory of vessels now comes before us, namely, the capability of forming rafts or life-belts, which will float under any circumstances. Here, again, every human invention of which I know has been anticipated by Nature. Take, for example, the familiar instance of the cork life-belt and the cork edgings of the life-boat. Both are constructed on the same principle, i.e. the maintenance of cells which are filled by air instead of water, and are impervious to the latter.

      The material most used for this purpose is cork, and life-belts constructed of it have long been in well-deserved use, the cork-bark having the property of holding much air and excluding water. Many of our life-boats are furnished with a broad and thick streak of cork, so that even if the boat be filled with water and upset, she will right herself and swim. I regret to say that many of the so-called “life-belts” which are offered for sale ought rather to be called “death-belts,” they having been found to be filled with hay and straw, with only a few shavings of cork just under the covering of the belt.

      Indeed, so buoyant is this substance that a very efficient belt can be made by stringing together three or four rows of ordinary wine corks, and tying them round the neck like a collar. Under these circumstances it is simply impossible to sink, and though any one may collapse from exhaustion, drowning is almost out of the question. The now well-known cork mattress, which is used in many ships, is another example of the same principle.

      Lately there has been invented a “life-collar,” which possesses similar advantages, but occupies less space when not wanted. It is nothing more than a tube of caoutchouc, which can be inflated at pleasure, and tied round the neck. The ordinary life-belt goes round the waist, and needs much more material without obtaining a better result, which is simply the keeping of the mouth and nostrils out of the water.

      Perhaps the most buoyant of living beings is the Portuguese Man-of-war (Physalis pelagicus), which floats on the surface of the ocean like a bubble. It can at pleasure distend itself with air and float, or discharge the air and sink.

      Now, there is a very remarkable swimming dress, which, though not entirely invented, was at least perfected by Captain Boyton, and which, as it enabled the wearer to cross from France to England under rather unfavourable circumstances, is clearly a most valuable invention.

      Whether the inventor knew it or not I cannot say, but the Boyton life-dress is simply a modification of the Physalis, being capable of dilatation with air at will.

      So much for the individual life-belt, and we will now pass to those which are intended to sustain more than one individual. It has almost invariably been found that when a ship has been wrecked on a rock, or stove in by the sea, that, although there may be plenty of boats, there is great difficulty in getting them into the water rightly.

      Now, if parts of the ship itself could be made of materials which could not be sunk except by enormous pressure, and which might be released by a touch if the vessel were sinking, it is evident that many lives would be saved which have now been lost.

      And if such movable parts of the vessel were supplied with water and provisions in air-tight cases, there is no doubt that the number of “missing” ships would be very greatly diminished. I remember an instance where a yacht was “hung up” on a mud-bank, whence there was no escape, for twenty-four hours, and there was one sandwich on board to be divided among the owner, two men, and a boy. Of course the boy had the sandwich, and the men sustained themselves as well as they could with tea, of which there was, fortunately, a canister on board. As it was, they were some thirty-six hours without food.

      After such an experience the owner had special lockers made in the yacht and her boat, containing biscuit, potted meats, water, wine, spirits, tobacco, tea, an “etna” for heating the water, and matches. Of course these were on a smaller scale in the boat; but several thick rugs were also stowed away, in case of being separated from the yacht at night. It so happened that they were never needed; but the sense of security which they imparted was worth ten times the expense and trouble, which included a careful inspection of all the stores before each voyage.

      In Nature there is just such a raft as is needed, capable of carrying a heavy freight, and which cannot be upset. And it is rather remarkable СКАЧАТЬ