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Page:Popular Science Monthly Volume 35.djvu/706

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THE POPULAR SCIENCE MONTHLY.

bergs, and icebergs of enormous size, which it is easy to avoid except in the frequent fogs of the summer months. These icebergs break from the immense glaciers bounding Melville Bay and Kennedy Channel, which occasionally rise two hundred feet above the water. It is apparent that the bergs breaking off irregularly might, through a bulky form of the submerged part, attain a still greater height. Hayes mentions a berg over three hundred feet high in the "north water"; the Proteus on her last trip sighted one a hundred and fifty feet high, six miles long, and a little more than a mile wide. These immense bergs are most important agents in breaking up the ice-fields in early spring, for, being propelled by deep under-currents, their motion is often contrary to that of the floe ice moved by the wind and surface currents.

The wind also plays an important part, a southwest gale sending the packs and hummocks upon the edge of the fast or land ice, and crushing it for some distance, after which any northerly wind disengages the free ice, leaving an open space, called the inshore lead, which the earliest whalers always follow. It is, of course, dangerous, as a south wind sends the pack back, and imprisons if it does not crush them. In July the quicker way through "the middle passage" of the Melville Bay pack is used, as the ice is then comparatively harmless, although vessels are sometimes nipped and rather severely handled.

No stronger vessels than those of the Dundee whalers are built; they are from four hundred to one thousand tons displacement, have powerful, well-secured engines to resist the shock of ramming or stoppage of the propeller by ice, and are built with an eye to the easy and rapid replacement of rudder, propeller, and propeller-shaft if damaged, these parts being carried in duplicate. Above all other considerations, they possess strength for ramming as well as resistance to lateral pressure when nipped.

Another very important feature is that the bow shall have considerable inclination, which permits the vessel, when ramming very heavy ice, to lift slightly and slide on it, thus easing the shock and assisting the cutting action of the bow with the downward crushing weight of the ship. In this way it is possible for these steamers at full speed to ram ice over twenty feet thick, and receive no immediate incapacitating damage.

If the ice is not too heavy, the shear-like rise and fall of the bow is repeated several times as the vessel steams powerfully ahead until her headway is checked. The difficulty then is to extract the ship from the dock she has cut by her advance: the floes press on her sides, cakes of ice and slush fill her wake, and there is nothing but the ice-hampered propeller with which to overcome her inertia and draw back out of the nip. Frequently this is insufficient, and the ship may be crushed.