POISON GAS

Greymouth Evening Star, 8 May 1936, Page 2

POISON GAS

FOR A SEA WORM. LONDON, March 24. For nearly 20 years experts have been investigating the ravages caused to timber, metal and concrete structures when immersed in sea water. To-day the Stationery Office publishes the results of this long research. Hundreds of different materials have been exposed, some for ten years, in many parts of the Empire to the action of sea air and water.

The reports states that damage to timber in sea-water is mainly caused by the ship-worm, or Teredo. This is a. niolusss which burrows with its shell, taking the sawdust into its body. It was the ship-worm that brought disaster upon Columbus’s fourth voyage by piercing his ships I “with worm-holes like a beehive. n - Impregnation of timber with poison has been found the best defence, and the best method, it is stated, is to dissolve ,an arsenical compound in creosote and force it into the timber. The most efficient, poison is one kno.wn as “D.M.,” which was used as a. poison gas during the war. Even more damage is done in some situations by the Limnoria, a minute animal allied to shrimps and lobsters, against which no effective protection has yet been found. Bars of 14 different materials were used for testing the corrosion of iron and steel. 'rhe results showed that the popular idea that corrosion is more severe under half-tide conditions is not always correct.

Except- at Colombo, the completely immersed bars lost more heavily in weight than those exposed at half-tide level. The best resistance was found to be from steel containing 36 per cent, of nickel. Nearlyl 500 reinforced concrete piles also were exposed, some at Sheerness and others on the Gold Coast of Africa. The experiments, among them the - addition of volcanic rock as a preservative, have been going on for five years, and are to ba continued for the same period, when a report will be issued.