SCIENTIFIC AND USEFUL.

New Zealand Graphic, Volume VIII, Issue 36, 12 September 1891, Page 361

SCIENTIFIC AND USEFUL.

IHE PLANET MERCURY. OrsEKv \tiox-made during the recent transit of Mercury by Mr J. K Winder, Detroit, convince him that the planet is surrounded by a dense atmosphere, which in a more attenu ated state, extends fur two or three hundred miles beyond his surface. The appearance of the spectrum also indicated the presence of aqueous vapour in the atmosphere of Mercury. A POWERFUL PROJECTILE. The British naval authorities are exhibiting with pride and satisfaction a projectile which, fired from a 110 ton gun, passed in succession through a 20 inch steel plate. 8 inches of iron, 20 feet of oak balks, 5 feet of granite and 11 feet of concrete, being finally staid in its path of destruction by a mass of brick masonry, into which it made its way to a depth of three feet. That projectile must have been well made, and of good metal. ANIMALS AND PLANTS. A curious and intimate relationship exists between some animals and plants, especially in tropical countries, where the struggle for existence is so fierce. One plant, known as the bull's horn acacia, of Central America, provides a species of ant not only with food and drink, in the shape of tiny egg-like bodies upon its leaves, and a sweet liquid contained in special wells on the stalk, but in addition it furnishes a tenement for the ant in the hollow spines with which it is armed. In return for these favours the ant protects the acacia from its enemies. PINEAPPLE CURE FOR DIPHTHERIA. One of my children was down with diphtheria and was in a critical condition. An old man who heard of the case asked if we had tried pineapple juice. We tried it and the child got well. I have known it tried in hundreds of cases. I have told my friends about it whenever I heard of a case and never knew it to fail. You get a ripe pineapple, squeeze out the juice and let the patient swallow it. The juice is of so corrosive a nature that it will cut out diphtheritic mucus, and if you will take the fruit before it is ripe and give the juice to a person whose throat is well it makes the mucous membrane of his throat sore. CAST-IRON TUNNELS FOR RAILROADS. Two tunnels of cast iron for an electric railway have been bnilt in London and put in operation for rapid transit. They are three miles in length and lie between forty and sixty feet below the surface of the city’s streets. The tunnels for the up and down lines are formed of cast-iron from beginning to end, save where the stations are built and their diameter is ten and one-half feet, the tubes being formed of rings one foot seven inches long, made in sections and bolted together. The tunnels were driven by means of a short cylinder, a trifle larger in its inner diameter than the exterior diameter of the cast-iron tunnel lining. This cylinder has a cuttiug edge and is forced forward by hydraulic jacks, butting a circular way into which the lining plates are fitted, the narrow space between the lining and the soil being filled with lime and cement forced in under high pressure. In their course the tunnels pass beneath the bed of the Thames and through the bed ot an old water-course, where loose, wet gravel offered some trying obstacles to be overcome. THE SWALLOW-SNAKE. The London Graphic is responsible for the following :—A particularly interesting serpent among those interested is the ‘ swallow- snake,' so called because, when the inclination seizes him, he takes his tail in his mouth, swallowing some of it, and thus transforms himself into a hoop, which rolls along with extreme velocity in pnisuit of prey. Judging from the illustration the chief occupation of the swallowsnake is to chase bicyclists along the roads of India, always overtaking the rider, unless he chances to have a bigger wheel than the snake can form. A 15 foot swallowingsnake, giving a wheel diameter of about five feet, can catch any bicyclist in India. From the description the swallowsnake mast be nearly allied to the American hoop snake, which, as is well known, takes its tail in its mouth ami chases boys out of meadows, the swallow snake, though, appears to be non-poisonous, in singular contrast with the nature of the hoop snake, which, when angered, is poisonous throughout its entire length, as we demonstrated in the case of the hired man who struck recklessly with a hoehandle at a hoop snake rolling past him, the hoehandle immediately swelling np to the size of a man's leg. MIND PICTURES. The uses to which the power of mental visualisation are put are most interesting. It is, as a rule, well developed in painters, some of whom are able to paint a portrait after seeing the subject but once. Dore, for one, possessed this faculty. His memory of anything he had once seen was marvellous, and be seemed to work at night as if the scenes he had made note of during the day were still before his eyes. After once driving through Windsor Park, he knew by heart every tree he had glanced at, and said that he could draw all from memory. Chess players of note have the faculty of visualising the board in their minds, and are thus enabled to play many games simultaneously blindfolded. One of the great chess players could play twelve games at once without seeing the board. He expressly stated that he had before him a perfectly vivid picture of each board which altered instantaneously as each move was male, and thus remained printed on his mind till another move again changed the situation. Some persons see mentally in print every word that they hear or which they s|>eak. < »ne states man assured Galton that a certain hesitation in utterance which he has at times is due to his being plagued by the image of his manuscript speech with its original eraanreand corrections. He cannot lay the ghost, and he puzzlein trying to decipher it.