Scientific Useful

New Zealand Graphic, Volume XXXVII, Issue 5, 4 August 1906, Page 34

Scientific Useful

THE MAGNETIC KNIFE. Most sailors carry a sheath-knife, and no fisherman is without one when a trawler goes to sea. But it is only just beginning to be recognised what risk to shipping may be involved in the practice. It appears that knives of a highlymagnetised kind are nowadays being sold in large numbers to seafarers, and that some of these instruments are so magnetic that if the wearer brings them within 18 inches of the compass-bowl he may defleet the needle fully two points either way. Quite recently there have been an exceptional number of fatalities to steam trawlers, and people are speculating as to how far the magnetised knife may be responsible for stranding attributable to deviation from the correct course. The matter is regarded as so serious that the secretary of the Grimsby Steam Fishing Vessels’ Insurance Company has issued a formal notice to masters, in which he points out that, while they cannot always prevent these knives from being carried by members of their crews, they must stringently direct that no knife shall be worn by any person who is steering the vessel, or who is on the look-out in the bridge-house. A hope is added that manufacturers will see the importance of producing knives which shall be non magnetic, and therefore incapable of producing the risks to which the circular draws attention. FLYING SNAKES. Although the alleged flying power of certain Malay frogs is now generally considered to be a myth, according to Mr. R. Shelford, who recently read a note on the subject before the London Zoological Society, three tree-snakes from Borneo are stated by the natives (and native testimony has very generalIv at least, a foundation of truth) to be possessed of the power of taking flying leaps from the boughs of trees to . the ground. The snakes in question, which belong to two distinct groups, are respectively named “Chrysopela ornata,” “C. chrysochlora,” and “Dendrophis pictus.” In all three of these, the scales on the lower surface of the body are provided with a suture or hinge-line on each side; and by means of a muscular contraction these scales can be drawn inwards, so that th-.* whole lower surface becomes quite concave, and the snake itself may be compared to a rod of bamboo bisected longitudinally. By experiments on “C. ornata”it was seen that the snake when falling from a height descended not in writhing coils, but with the body held stiff and rigid, and that the line of the fall was at an angle to a straight line from the point of departure to the ground. In the author’s opinion it is highly probable that the concave ventral surface of the snake helps to buoy it up in its fall; as it can be shown that a longitudinally bisected rod of bamboo falls more slowly than an undivided rod of equal weight.—“ Knowledge.” ♦ ♦ ♦ DREAMERS HAVE NO MEMORY. No one is ever surprised in a dream. A man dreaming is at one moment bathing in the sea and at the next moment soaring in a balloon, but the sudden and inexplicable change does not surprise him. Nor is he surprised to meet in the flesh friends long dead; nor is he surprised to find himself doing deeds that really are beyond him, as winning the love of notable beauties, or knocking out champion heavy-weights, or, if politically inclined, besting in debate Mr. Chamberlain or Sir Henry, Campbell-Bannerman. No one, says a writer in “Popular Science Siftings,” is ever surprised in a dream, and live reason is that dreamers have no memory. In real life, to be pursued through the streets by a lion would be astonishing, but this accident would be accepted in a dream as horrible but quite common* place, the memory not being there to gay that it is unheard of tor Hong to

pursue meu iu cities. In the same way, in dreams, men are not surprised to find themselves ballooning, because they do not remember that they were never up in a balloon before, and they are not surprised to find themselves conversing wit ii dead people, because they do not remember that these people are dead. There can be no surprise without memory, and it is because meu have no memories in their dreams that they then accept calmly and credulously the most amazing and incredible things. THE ELECTRIC PERIL. Universal blindness, according to an “X-ray and therapeutic expert” in Chicago, is the danger threatening mankind because of their audacity in utilising the electric force of the universe. This prophet of woe, Dr. H. Preston Pratt, was called to give evidence for a young lady who has for nearly four years been partially blind and paralysed owing to an electric current passing into her body “through the atmosphere” from the wires of the Union Traction Company, and who accordingly claimed £lO,OOO damages. The doctor sets forth “that corroding effects have been discovered by eye specialists to proceed from the millions of dynamos now at work in every corner of the civilised world. Day and night we are never free from their baleful influences; and the eyes—the most delicate part of the human body—are the first to suffer.” COOKING FOOD. The object of cooking food, apart from the gustatory effect of bringing out the pleasant flavours, is to increase its digestibility by breaking up its fibres into lengths more convenient for the digestive organs to deal with. In some instances meat would be quite as digestible without cooking; and BrillatSavarin declared that it was not unpleasant to the taste. But if cooking is only to break up th? fibres the same effect might be produced by extreme cold: and it has been shown that meat can in this way be “cooked” by liquid air. A smaller degree of cold will produce similar effects on vegetables and Dr. Ephraim Cutter speaks in the most appreciative terms of' a “frost-bitten potato.” It was. he says, shrunken, soft. limp, ami elastic. It looked dark as if rotten, and yet there was no dead or deeaving odour. Under th * microscope its starch grains were shrunken, cracked, and fissured in the long and short diameters, wrinkled, and they polarised light beautifully. From all of which, as well as from the evidence of taste, Dr. Cutter thinks that such potatoes might be eaten without harm. Cranberries and onions were also frozen and tested: but though they might have been eatable, and were at any rate tasted, it is not quite certain from the microscopic examination of the grains whether they were “cooked” in the scientific sense.