AID FOR AVIATORS

Evening Star, Issue 22805, 13 November 1937, Page 9

AID FOR AVIATORS

COLOURING THE OCEAN Georges Claude, whoso neon lights glow with a hard, red relentlessness on very main street, rose before the French Academy of Sciences recently to tell its members how he would make it possible to find aviators who have fallen into the sea and who may still be afloat, says the ‘ New York Times.’ “ I think it would bo possible for the ill-fated aeroplane to produce a huge coloured spot in the ocean which would be seen from afar and which would endure for a long time, oven in a storm,” remarked the ingenious Claude by way of introduction. One part of many an organic dye is enough to stain ten million parts of water. Claude holds that fluorescein would be the best. Chemists know it as resorcinol phthalem._ It comes in red crystals which stain water a yellowish green. Last January some tests were made by Claude on. the French submarine Thetis. A kilogram (2.2 pounds) of

acid fluorescein mixed with powdered cork and thrown overboard off the peninsular of Giens made an irregular bright green spot about 650 ft in diameter. The spot could easily be seen from an aeroplane at a distance of about two and five-tenths miles, especially when the sun was behind the observer. After three and a-half hours the spot was dissipated by a storm. Fluorescein is easily discoloured by sunlight. A solution of one part in one million begins to lose its hue in about three hours. Claude decided that the solution must be continuously renewed and at the surface. So he packed his chemical in little perforated cylinders half an inch in diameter and three-quarters of an inch long. The amount of chemical in each cylinder was 0.2 gram. Cotton plugs at the ends retarded, the outward flow of the solution. Claude says that one of these cylinders is good for 12 hours and even for 24 if special packing be adopted. He

estimates that ' 50,000 cylinders and about 22 pounds of fluorescein would be required for an air liner plying between South America and Europe, but that a smaller aeroplane could do with a smaller supply. Claude would release the cylinders in four perforated boxes, one after the other, so as to avoid clustering and to produce the largest possible -spot. The boxes would be kept afloat by cork. After a time the water would flow in. The boxes would bo prevented from sinking lower than two to six feet by ropes along which they would slide and which would be attached to the cork floats. RESULTS OF HIS TEST. As each box bobbed up and down in the water the little cylinders would slip through the space deliberately left between the rope and the hole through which it passes in the box, rise to the surface, and discolour the water. Thus the spot would be prevented from fading. Claude told the academicians that he tried this invention in the submarine Le Venguer off Cape Side last April. Two _ kilogrammes (4.4 pounds) of chemical wore divided into four batches consisting of 2,600 cylinders each. The weather was fine and the sea moderate. From the conning tower of the submarine (about 17ft above water) the spot, still small, could be seen from a distance of three-tenths of a mile. The submarine plunged beneath the waves an hour after the boxes were released, and the observer noted that the water was deeply stained. Claude attributes this effect in part to some bad cylinders (one-third of the whole lot) which liberated fluorescein too quickly. When the submarine came up again the spot, now much larger, could be seen from a distance of a mile and a-quarter despite the small angle of vision. Aviators also saw the spot plainly from all angles.