Water Twister

Few people have ever studied a tornado, fewer still its nautical equivalent, a waterspout. First instinct of those who have seen this terrifying natural phenomenon, which links heaven and earth with a dark, serpentine Jacob's ladder, is to get out of its path.

Last week the National Geographic Society reported that its South American survey plane was cruising from Miami to Havana when: "Pilot Hawkins, to avoid an angry black cloud, veered to port. Then, to our amazement, there quickly dropped from the north end of the storm cloud a thin writhing black column of a waterspout. In a few seconds, as we watched, it grew into a black, whirling corkscrew at least 600 feet high and probably 50 feet or more in diameter. ... As it grew in size ... it took the shape and appearance of a great snake, spray and mist rising in clouds from where its tail lashed the sea. Yet its writhing edges were clean-cut as a broad band of black ribbon. ... It was exactly seven minutes from the time the spout first formed until it faded into the black depths of the moving squall."

During this time the plane did not retreat from the twister but impudently dodged about it. Trusting to powerful motors which drove them along at 127 m. p. h. the crew took photographs, copious notes.

Sailors cherish an ancient notion--a de-lusion--that, if a ship cannot escape a waterspout by moving out of its path, a shot fired into the column of water will cause it to collapse. Science has no record of this having actually been done, for the good reason that no cannon projectile (unless perhaps a large explosive shell timed exactly) would be big enough to disrupt the enormous vacuum which supports the water column.

Waterspouts and tornadoes are caused by a condition of unstable equilibrium in the atmosphere. A warm, damp air layer close to land or sea attempts to rise through a layer of cool, dry air. The warm air literally breaks a hole in the cooler air, rushes upward. Passing through the hole it assumes a whirling motion. The centrifugal force of the column develops a partial vacuum on the inside.

The dancing column of the waterspout, often a mile high, 200 ft. in diameter, carries a great volume of water which it sucks from the sea. Terrifying to seamen by virtue of the fact that the column whirls at the rate of 150 m. p. h., these twisters are seldom long lived. Tornadoes over land last longer, travel from 30 to 50 mi. Greatest in the U. S. was that of 1925 which stretched a ribbon of destruction across Missouri, Illinois, Indiana. In its wake were 695 dead and $16.500,000 worth of tangled, destroyed property.* Instead of transporting water, tornadoes carry chickens, small live stock, lumber, outhouses. Houses and barns in the path of a tornado are not blown down but explode. The vacuum column draws the air from around the house, the inside pressure forces the walls out.

*Tornadoes last week in Wisconsin and Minnesota killed five persons, wreaked $1,000,000 havoc.

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