SCIENTIFIC AND USEFUL.

New Zealand Graphic, Volume X, Issue 10, 11 March 1893, Page 224

SCIENTIFIC AND USEFUL.

MANUFACTURED GRINDSTONES. SCIENCE comes to the front in the manufacture of grindstones. The best now made are composed of a mixture of pulverized quartz, powdered flint, powdered emery and rubber. They outwear by many years any natural stone. THE COLOUR OF CARROTS. Where does the red colour come from ? The roots of the wild carrot are, so far as we know (says the Gardeners' Chronicle) not red, and we have lately examined several roots of the maritime variety, Dancus maritima, and they are not red. Still there is a tendency in the plant to produce a red colour, as occasionally the central flower of the umbel is of a deep purple colour, while all around are whitish. Why ’ The carrot has been known from the earliest times, and its origin from either of the two foims above mentioned is only a matter of assumption. There are other species from which it might have descended. AN EXTRAORDINARY GAUGE. An extraordinary electric railway, so far as the gauge is concerned, is projected between Brighton and Rottingdean. A Bill for powers to construct is to be introduced into Parliament next session. This railway, which will be nearly four miles in length, will commence at Paston Place, Brighton, and proceed along the beach and foreshore ‘ between high and low water mark at a distance of about 100 yards from the cliff’ to Rottingdean. From the termination of the railway a jetty is proposed to be constructed for a distance of 200 feet into the sea. The railway will be constructed on the extraordinary ‘ gauge ’ of 24 feet. MR EDISON’S NEWEST PHONOGRAPH. Mr Edison states that he expects soon to so perfect his phonograph that it will be able to deal with sounds inaudible by the human ear. Once captured by bis improved phonograph, these sounds will be returned to the listener intensified to a degree to make them easily audible. It is interesting to know that Piofessor Bell’s latest device of importance, the ‘ waterphone,’ for locating leaks in waterpipes, was suggested to him by observing a plumber’s ap prentice endeavouring to find a leak by means of a small steel rod which he held in his mouth and touched against the pipe. TYPES OF FINGERS. Herr Otto Moretus, in a recent article on ‘ The Art of Reading Character in the Hand,’ that is, to discover the chief characteristics of a person by the shape and general appearance of the hand, says that there are three types of fingers, and that these are of the highest importance in character-reading, because, in conjunction with the palm, they give the key to the whole character of an individual. These types he describes as: ‘ Fat fingers, broader at the ends than at the knuckles ; angular, knotty fingers, with the extremities of the same breadth as the knuckles, and conical fingers, with tapering tips. The first of these types shows that the individual is more inclined to the useful and practical than to the ideal; has a strong sense for the material, for physical strength, for industrial occupation, for the practice of the scientific, and, generally, a decided aversion to philosophy, poetry and metaphysics. Knotty fingers signify a preference for philosophy, the sciences, and logic. Men with such fingers, like the exact, the positive in science and life; they are inventive, and happy in turning their knowledge to account; therefore they have business talent, but seldom know any higher or more poetical flight. Men with conical, tapering fingers, are artistically gifted, and easily carried away ; they strive for social independence, and incline to the ideal in art and life.’ A COURTING AND FIGHTING CRAB. In his report, as surgeon naturalist of the Marine Survey of India, Dr. A. Alcock records some interesting observations on the little estuarine crab Gelasimus. The most obvious structural peculiarity of Gelasimus is the enormous development of one of the chelce or jaws in the male only, the chela! in the female being minute. In the colder months, at any rate, the males far outnumber the females. In a fully adult male the length of the large chela! is two and a half times the greatest length, and one and a half times the greatest breadth of the whole body, and 40 per cent, of the entire weight of the animal, and is coloured a beautiful cherry-red fading to a rose pink, the rest of the animal being of a dingy greenish brown colour. Dr. Alcock has been able to observe that, whatever other functions the great chela may serve, it also, in the species under consideration, is (1) a club used in the contests of rival males, and (2) a signal to charm and allure the females. This last function is particularly apparent. As one walks across the mud one first becomes aware of the presence of these crabs by noticing that the surface of the mud is everywhere alive with twinkling objects of a brilliant pearly-pink colour. Carefully watched, these prove to be the enormous chehe of a crowd of males of Gala.si.inus waving in the air, each little crab standing at the mouth of its burrow and ceaselessly brandishing its big claw. On closer observation, among every ten or so males a small clawless female can be seen feeding in apparent unconcern. If the female should approach the burrow of a male, the latter displays the greatest excitement, raising itself on its hindmost legs, dancing and stamping and frantically waving its beautifully coloured big claw. From prolonged watching, Dr. Alcock feels convinced that the waving of the claw by the male is a signal of entreaty to the female, and he thinks no one can doubt that the claw of the male has become conspicuous and beautiful in order to attract and charm the female. The second function as a fighting weapon, becomes appaient when in the general tournament one of the lival males approaches too close to another. The great claw is then used as a club, the little creatures making savage back-handed sweeps at each other.