Icebergs

Radio Record, Volume II, Issue 48, 14 June 1929, Page 31

Icebergs

Lecture from 4YA ee — eye

UNDER thé auspices of the. Otago W.B.A. Dr. Tochen, of the University of Otago, will deliver a lecture. from 4YA on Tuesday, June 18, at 7.30. No one will deny that icebergs are a menace to shipping. Sincé the world was shocked by the dreadful ‘Titanic disaster there have been several minor accidents due to the same cause. We are inclined in New Zealand to, underestimate the danger, since our shipping rarely enters the iceberg zones. . Ina recent cable message, however, one of these rare cases was reported-~a boat en toute from Oape Town to Auckland sighted a large iceberg when a few days out from South Africa, The danger has been diminished to some ¢xtent by improved steamship désign émhodying the use of many water-tight compartments, but naturally a removal of the cause of danger would be a more thorough and satisfactory solution to the problem. Besides this, the composition. and structure of these large masses of ice and their life history have attracted the attention of several notable scientists. For these and other reasons the "life and habits" of icebergs have been closely investigated’ and more especially since the war methods for locating and for destroying them have been studied principally in Canada, whose shipping has

been seriously embarrassed by their prevalence. icebergs are "born" towards the late summer round the edges of the huge icée-sheets surounding the polar continents. It may be recalled that Commandet Byrd’s hoat, thé City of New York, was carried away once when a huge block of the ice-sheet broke away from the parent body. The subsequent history of the icebergs depends largely on the ocean Currents and prevailing winds. Their occurrence is most frequently observed in the North Atlantic, where the steamers have for safety during the winter months to adopt a more southerly. course than the direct one followed the rest of the year. Icebergs are déceptive as to size, for as most people know the greater part of thet is submerged. Not a few would be surprised to know that only about one-tenth of thé volumé is visible. (The exact proportion can be reckoned from the felation that 100 ‘eubic feet of water expand on freezing to. form 109 cuibic feet of ice.) The problem of locating icebergs is not so difficult as that of destroying them. In fact. this latter problem has taxed the ingenuity of engineers and physicists very considerably, but it is now miaintained that a reliable and practi¢al method has been discovered and it is with this method that the lecturétte on Juné 18 will chiefly deal. It is manifestly impossible to desttoy icebergs until they are located and the obvious but not the easiest or safest. method of doing this is to keep a bright look-out for them in the regions where they are most dangerous. This method rather overlooks the danger to the small craft doing the scouting, which have to be specially eonstructed like the Russian Government’s icé-breakers, and the prevalence of fogs in these particular regions. The distance of the visual horizon is, in any case, strictly limited by the height of the observer above the sea level. Another method which suggests itself is to use some physical property of the iceberg to enable you to detect it from a& distance, for instance its low temperature, which is, of course, 0 degrees Centigrade, or its solidity. Actually both these properties have beén utilised, but it is the solidity together with a means of producing and recording suitable sound waves which has led to the best method of location. With this the lecturer will also deal.