SCIENCE OF THE DAY.

New Zealand Herald, Volume LXV, Issue 20136, 22 December 1928, Page 6 (Supplement)

SCIENCE OF THE DAY.

ELECTRICITY FROM FISH. Electric fish are those that give out electric shocks when an atempt is made to catch them. There are three known varieties; the torpedo, or electric ray, the electric catfish, and tho spotted stargazer. Professor Starr Jordan writes;' "In the winter of 1882 a tourist came to my office bearing a small ray or skate, of which he told a curious story. ' Seeing the little fish close to the shore, he stabbed it with a pocket-knife, and immediately felt a shock which momentarily paralysed his arm. The fish belonged to the family of torpedoes, or electric rays. The torpedoes are similar to the ordinary skate in appearance, but softer in body and more rounded in form. In all torpedoes the electric organ is the same in structure. It consists of a large patch of six-sided honey-comb-like cells some 400 in all in the larger species. These are situated under the skin on each side of the head, below and behind the eyo. Tho torpedo yields a quick, sharp shock when touched, and tho shock is easily carried along a metallic conductor, such as a knife or a spear. Although disconcerting, ths shock is not dangerous. The exercise of tho power soon exhausts tho fish and a rest period is needed. Tho electrical apparatus of the electric catfish is composed of small structures hidden under tho surface of the skin along the whole body. A remarkable feature of the whole family of star-gazers is tho square, box-like head, with small eyes on top, so that tho fish cannot look sideways. Behind each eyo is a small electric battery. FYLING IN FOGS One of the great difficulties with which civil aviation is faced is that of maintaining a regular service under bad weather conditions. Tho problems arising under this category relate to control, navigation, and landing, but it is with the first of these that. a recent writer deals. When the pilot is deprived of his horizon the control of an aeroplane becomes exceedingly difficult, in spite of the information which can be supplied by such instruments as turn indicators. Generally, if the rudder can be operated so as to keep the aeroplane flying in a con-

stant direction, most of the difficulty disappears. It should bo noted, however, that observation of a magnetic compass is practically useless from this point, of view, owing to tho disturbances which arise from centrifugal force when the aeropiano departs from a straight course. For this reason, tho automatic rudder control developed at tho Itoyal Aircraft Establishment relies for its sense of direction on a free gyroscope, or " gyro azimuth." The control consists essentially of a pneumatic ram servo-motor, which operates an auxiliary rudder bar and is controlled by an air valve attached to the azimuth ring of a gyroscope. The gyro wheel is spun at high speed, and its axle is set along the line of the required compass course.! Deviation of the aeroplane from its course entails relative movement between the azimuth ring and the aeroplane, since the axle of the wheel maintains a constant direction in space. Tho consequent disturbance of the valve admits compressed air to one cylinder of the servo-motor and exhausts the other to atmosphere, thus causing the servo-motor to apply a correction to the rudder. GLASS THAT BOUNCES. Plass is the glass that will not break. It cannot be bought in tho shops, but Professor E. C. Baly, of Liverpool University, has blown .it, and. speaks with tho authority of a first-class scientific man of its properties. Fifty years ago glass tumbles were sold in Liverpool which could bo dropped on the floor without breaking, sometimes, and many kinds cf toughened glass have been mado since. But tho earliest kinds, and some of tho later ones, had a disturbing knack of splintering into small pieces if they were hv any moans chipped. Professor Baly's glass is mado by a new process first invented by Dr. Pollack, of Austria, and now improved to a point at which it can be moulded into shape, and can bo thrown on fo a stono floor without doing anyworse than bounce. The burglar cannot put through it, but the ultra-violet rays of sunlight can.