CONQUERING FOG

New Zealand Herald, Volume LXXI, Issue 21396, 20 October 1934, Page 7 (Supplement)

CONQUERING FOG

NEW DEVICE CONDENSES MIST

Years of research'-apparently have been rewarded by the discovery of a successful weapon against fog, the terror of the air and seas. When fog rolled in around the airport on the estate of Colonel E. H. 11. Green at Round Hill, Massachusetts, recently, it was chemically dissipated over a limited area by a method devised by Mr. Henry G. Houghton, a member of the research staff of the Massachusetts Institute of Technology at Cambridge, states the Literary Digest. The equipment used was simply a pipe 100 ft. long, suspended horizontally in the air about thirty feet above the ground, and fitted with elaborate nozzles of special design at frequent intervals along its length. To this pipe ran a feed line from a pump, which forced the chemical into it.

The engineers wore ready for the test for several weeks before fog came. As soon as it had completely enveloped the airport, the centrifugal pumps were started, spraying the chemical into the air. Within a few seconds the fog drifting through the curtain of falling chemical began to gather into large drops and descend like rain. In 'effect the curtain of chemical was straining the fog, for immediately a path of visibility approximately 100 ft. wide and thirty feet high began to open across the airport down the wind. On either side were walls of turbulent white vapour, but in the cleared area the ground was entirely free. The lane continued to open as though a huge, invisible plough were moving through the mist. Within three minutes buildings more than 2000 feet away were clearly revealed. The path was kept clear as long as the chemical curtain was operated. llie composition of the chemical used is being kept secret for the time being, pending further tests. It works by causing minute water drops, of which fog is composed, to condense into larger drops of such size that they can no longer float in air. Part of the secret is in the construction of the nozzles of the spray, for the chemical solution itself must be broken into droplets and will not work if these are either too large or too small. Mr. Houghton has studied fog for several years, in order to learn exactly what causes it, and he is believed to have been the first to photograph the minute water droplets of which all fogs consist. These are sometimes as small as onc-twenty-five-thousandth of an inch in diameter, only slightly larger than the wave-length of red light. Such droplets must have a nucleus upon which to form, either a large ion, a microscopicjrrain of dust or other particle. Mr. .noughton says he found that most sea fogs form on tiny crystals of salt thrown into the air by spray.