this vessel as much common salt as it would take up, whereby the density of the fluid was so much augmented that it opposed a resistance to the descent of the egg after it had passed through the unadulterated water, which he had carefully poured upon the briny solution, the transparency of which, remaining unimpaired, did not for a moment suggest the suspicion of any such impregnation. The good housewife, upon the same principle, uses an egg to test the strength of her brine for pickling.
Every one has heard of the power which bleaching gas (chlorine) possesses in taking away color, so that a red rose held over its fumes will become white. The lecturer, referring to this fact, exhibited two pieces of paper; upon one was inscribed, in large letters, the word "Proteus;" upon the other no writing was visible; although he assured us the same word was there inscribed. He now dipped both pieces of paper in a solution of bleaching-powder, when the word "Proteus" disappeared from the paper upon which it was before visible; while the same word instantly came out, sharp and distinct, upon the paper which was previously a blank. Here there appeared another contradiction: the chlorine in the one case obliterating, and in the other reviving the written word; and how was this mystery explained? Easily enough! Our ingenious philosopher, it seems, had used indigo in penning the one word which had disappeared; and had inscribed the other with a solution of a chemical substance, iodide of potassium and starch; and the action which took place was simply this: the chlorine of the bleaching solution set free the iodine from the potassium, which immediately combined with the starch, and gave color to the letters which were before invisible. Again – a sheet of white paper was exhibited, which displayed a broad and brilliant stripe of scarlet – (produced by a compound called the bin-iodide of mercury) – when exposed to a slight heat the color changed immediately to a bright yellow, and, when this yellow stripe was crushed by smartly rubbing the paper, the scarlet color was restored, with all its former brilliancy. This change of color was effected entirely by the alteration which the heat, in the one case, and the friction, in the other, produced in the particles which reflected these different colors; and, upon the same principle, we may understand the change of the color in the lobster-shell, which turns from black to red in boiling; because the action of the heat produces a new arrangement in the particles which compose the shell.
With the assistance of water and fire, which have befriended the magicians of every age, contradictions of a more marvelous character may be exhibited, and even the secret art revealed of handling red-hot metals, and passing through the fiery ordeal. If we take a platinum ladle, and hold it over a furnace until it becomes of a bright red heat, and then project cold water into its bowl, we shall find that the water will remain quiescent and give no sign of ebullition – not so much as a single "fizz;" but, the moment the ladle begins to cool, it will boil up and quickly evaporate. So also, if a mass of metal, heated to whiteness, be plunged in a vessel of cold water, the surrounding fluid will remain tranquil so long as the glowing white heat continues; but, the moment the temperature falls, the water will boil briskly. Again – if water be poured upon an iron sieve, the wires of which are made red hot, it will not run through; but, on the sieve cooling, it will run through rapidly. These contradictory effects are easily accounted for. The repelling power of intense heat keeps the water from immediate contact with the heated metal, and the particles of the water, collectively, retain their globular form; but, when the vessel cools, the repulsive power diminishes, and the water coming into closer contact with the heated surface its particles can no longer retain their globular form, and eventually expand into a state of vapor. This globular condition of the particles of water will account for many very important phenomena; perhaps it is best exhibited in the dew-drop, and so long as these globules retain their form, water will retain its fluid properties. An agglomeration of these globules will carry with them, under certain circumstances, so much force that it is hardly a contradiction to call water itself a solid. The water-hammer, as it is termed, illustrates this apparent contradiction. If we introduce a certain quantity of water into a long glass tube, when it is shaken, we shall hear the ordinary splashing noise as in a bottle; but, if we exhaust the air, and again shake the tube, we shall hear a loud ringing sound, as if the bottom of the tube were struck by some hard substance – like metal or wood – which may fearfully remind us of the blows which a ship's side will receive from the waves during a storm at sea, which will often carry away her bulwarks.
It is now time to turn to something stronger than water for more instances of chemical contradictions. The chemical action of certain poisons (the most powerful of all agents), upon the human frame, has plunged the faculty into a maze of paradoxes; indeed, there is actually a system of medicine, advancing in reputation, which is founded on the principle of contraries. The famous Dr. Hahnemann, who was born at Massieu in Saxony, was the founder of it, and, strange to say, medical men, who are notorious for entertaining contrary opinions, have not yet agreed among themselves whether he was a very great quack or a very great philosopher. Be this as it may, the founder of this system, which is called Homœopathy, when translating an article upon bark in Dr. Cullen's Materia Medica, took some of this medicine, which had for many years been justly celebrated for the cure of ague. He had not long taken it, when he found himself attacked with aguish symptoms, and a light now dawned upon his mind, and led him to the inference that medicines which give rise to the symptoms of a disease, are those which will specifically cure it, and however curious it may appear, several illustrations in confirmation of this principle were speedily found. If a limb be frost-bitten, we are directed to rub it with snow; if the constitution of a man be impaired by the abuse of spirituous liquors, and he be reduced to that miserable state of enervation when the limbs tremble and totter, and the mind itself sinks into a state of low muttering delirium, the physician to cure him must go again to the bottle and administer stimulants and opiates.
It was an old Hippocratic aphorism that two diseases can not co-exist in the same body, wherefore, gout has actually been cured by the afflicted person going into a fenny country and catching the ague. The fatality of consumption is also said to be retarded by a common catarrh; and upon this very principle depends the truth of the old saying, that rickety doors hang long on rusty hinges. In other words, the strength of the constitution being impaired by one disease has less power to support the morbid action of another.
We thus live in a world of apparent contradictions; they abound in every department of science, and beset us even in the sanctuary of domestic life. The progress of discovery has reconciled and explained the nature of some of them; but many baffle our ingenuity, and still remain involved in mystery. This much, however, is certain, that the most opposed and conflicting elements so combine together as to produce results, which are strictly in unison with the order and harmony of the universe.
DESCENT INTO THE CRATER OF A VOLCANO. 14
A descent into the Crater of the Volcano of Kilauea in the Sandwich Islands, may be accomplished with tolerable ease by the north-eastern cliff of the crater, where the side has fallen in and slidden downward, leaving a number of huge, outjutting rocks, like giants' stepping-stones, or the courses of the pyramid of Ghizeh.
By hanging to these, and the mere aid of a pole, you may descend the first precipice to where the avalanche brought up and was stayed – a wild region, broken into abrupt hills and deep glens, thickly set with shrubs and old ohias, and producing in great abundance the Hawaiian whortleberry (formerly sacred to the goddess of the volcano), and a beautiful lustrous blackberry that grows on a branching vine close to the ground. Thousands of birds find there a safe and warm retreat; and they will continue, I suppose, the innocent warblers, to pair and sing there, till the fires from beneath, having once more eaten through its foundations, the entire tract, with all its miniature mountains and woody glens, shall slide off suddenly into the abyss below to feed the hunger of all-devouring fire.
No one who passes over it, and looks back upon the tall, jagged cliffs at the rear and side, can doubt that it was severed and shattered by one such ruin into its present forms. And the bottomless pits and yawning caverns, in some places ejecting hot steam, with which it is traversed, prove that the raging element which once sapped its foundations is still busy beneath.
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