The advancing limit of Arctic ice, having in its train an endless procession of masses drifting down from the North, reaches the northern average limit of the Gulf Stream in the month of April, and having spread itself along this line both East and West of the 50th meridian of longitude, the ice disintegrates and rapidly disappears. Still, after reaching this limit of southward movement, many bergs, on account of their deep immersion, find their way to the westward even within the current of the Gulf Stream.
The locality in which ice of all kinds is apt to be found during the months of April, May, and June lies between latitude 42 degrees 45 minutes and longitude 47 degrees 52 minutes west of Greenwich. Here the Gulf Stream and the Labrador current meet; here the movement of the ice is influenced sometimes by the one and sometimes by the other of these currents; and here in latitude 41 degrees 46 minutes and longitude 50 degrees
14 minutes the "Titanic" came to grief.
A huge iceberg, in the shape of a ship’s sail, floats in the North Atlantic, in a photo published in 1912. Credit: Scientific American, April 27, 1912
The Menace of the Iceberg.
It is the huge mass of an iceberg that the mariner has most to fear. While it may vary in size, an ordinary iceberg will measure from 60 to 100 feet to the top of its walls, and it will have spires or pinnacles towering from 200 to 250 feet above a base that may be from 300 to 500 yards in length. Only one-eighth or one-ninth of the entire mass lies above water. Mass, let it be borne in mind, is a different quantity from height. Hence, the statement sometimes found in books that the depth of a berg under water may be from eight to nine times the height above water is incorrect. It is possible to have a berg as high out of water as it is deep below the surface; for if we imagine a large, solid lump of any regular shape, which has a very small sharp high pinnacle in the center, the height above water can easily equal the depth below. The Hydrographic Office has recorded the case of a berg, grounded in the Strait of Belle Isle in sixteen fathoms of water, that had a thin spire about 100 feet in height. Often the bergs are so nicely balanced that the slightest melting of their surfaces causes a shifting of the center of gravity and a consequent turning over of 'the mass into a new position.
Disintegration occurs very rapidly. On the coast of Labrador in July and August, when bergs are packed thickly together, the noise of rupture is often deafening. When they are frozen, the temperature is very low, so that on exposure to a thawing temperature the tension of the exterior differs from that of the interior. In other words, the berg becomes like a huge Prince Rupert's drop, which, as every one knows, is a drop formed by allowing molten glass to fall into cold water. It is said that the concussion of gun fire will sometimes break up a berg, so unequal is the tension within and without. During the day, water, the result of melting, finds its way into crevices. At night it freezes, expands, and splits the berg. The greater the splitting action the more rapid is disintegration, because new surface is exposed. Were it not for these circumstances, large bergs would remain intact years before they melted completely away.
The Queer Shapes of Icebergs.
Not only is the huge mass of an iceberg a source of danger, but its eccentric shape is as well. The weird pinnacles, spires, domes, minarets, and peaks, that remind one of castles fashioned by some genius for the pleasure of some whimsical fairy princess, find their counterpart in unseen, outlying spurs that project under water and that are fully as dangerous as any reef. The United States Hydrographic Office has called attention to the accident sustained by the British steamship "Nessmore," which ran into a berg and stove in her bows. When she was docked a long score was found extending from abreast her fore rigging all the way aft, just above the keel. Four frames were broken, and the plates were almost cut through. As there was clear water between the ship and the berg after the first collision, it was evident that the ship had struck a projecting spur after her helm had been put over.