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July, 1917 ment they should pay, and then collect a toll from each vessel going through, that also to be determined by the size of the vessel. This should take care of the upkeep expenses. It will certainly be economical to keep ice breakers in constant service. Even the government of the United States ought to be called in to help maintain them after the gov- ernment has got rid of the war expenses. Obstacles Are Insuperable By “Open Water” HAVE noted the suggestion of reducing the opening of navigation to a schedule by the employment of ice- breakers and your invitation to join in a free discussion thereof. I am disposed to think that a little further study of the problem might induce a modification of this view. First, as to forcing an opening. It should be borne in mind that the ice which causes the trouble is not formed in situ. Where ice fields are formed naturally by freezing, it is the experience of all, I think, that the mere breaking of a channel by boats. built or suited for the purpose is no very difficult matter. Nor is there much difficulty in maintaining such channels provided the ice field does not shift. Nor will much difficulty be found by freighters in navigating such channels provided the channel is broken out to a sufficient width and the ice well broken up. Every passage through such a channel makes each subsequent passage easier, provided again that passages are not too far apart in time and extreme temperatures do not continue too long. With fresh water at or about freezing point, as it necessarily is in the presence of extensive ice fields, especially if the current, if any, is of ‘low velocity and little substitution of water at slightly higher temperature though of the same density occurs, a very few hours of sustained low temperature is sufficient solidly to reunite the whole mass. These features are familiar to all who have had experience with winter and early spring navigation in waters where fields are formed naturally and _ locally and cannot shift. Please note carefully, however, the conditions named. How the Ice Fields Are Formed As a matter of fact, however, the fields which cause the principal difficulty are not so’ formed. They are the aggregate of innumerable smaller masses formed along shore, or in quiet water under the lee of the land and later carried off shore by a shift of wind, or in the open lake, and gradually assembled by the prevailing winds towards one end of the lake or the other and anchored by windrowing and grounding, or by contracted channels and. islands as in the Straits, and gradually become firmly bonded together by freezing. This mass increases in depth too by pressure due to high winds and the accretion from below due to continually lowering temperature of the water underneath as maximum density is approached, and the added weight of snow above. This last is, by the way, the feature which makes ice encountered after a winter of heavy snow so difficult to deal with because when softened by sun, rain, or moistened by being broken up, it becomes mushy on the surfaces and packs so closely either to the ship or other floes that it cannot be worked through. The most powerful ice-breaker, which can deal without difficulty with hard ice, even though heavy, will stall in such fields. Now, this is the condition exactly which is met with in Whitefish bay, Duluth, Buffalo and the Straits. In Whitefish bay and at Buffalo the situation is aggravated by the natural current of the Soo and Niagara rivers which tends to draw the ice more and more compactly into the rivers and by the prevailing winds in the rear THE MARINE REVIEW 241 continually building the windrows higher and_ higher. Along the outer edges of the field the floes are more or less disunited due to wave action. When a shift of wind occurs this drift is carried out perhaps, only to be hurried back by another shift and not only be piled windrow on windrow but also driven underneath, so that the field continually builds in extent and depth and explains why the fields are generally more difficult to negotiate as the lake is. approached. There will always be found a fringe of varying width, perhaps several miles, along the outer edge, which is adrift due to the wave action referred to, and may be penetrated, but back of this is the solid mass of ice. Why Channels Close So Quickly Now, it has been observed by those who have had experience in fields of this nature, exposed over large areas to the action of winds, that tremendous lateral pressures exist, so great in fact that under the influence of long-continued gales the field formation is unable to resist the crushing effort. Hence the formation of leads or open channels which are promptly closed again with the shift of wind. Thus, even when a channel, or rather passage, has been forced, say by an _ ice-breaker, the lateral pressure is so great that it closes, perhaps immediately. The writer has often noted that where a passage or open lead has been thus closed the ice body at that point could not again be forced, the inertia of the whole field being so great that the thickness at that point was greatly increased, just as bar of iron may be upset by applying end pressure. This movement is well known and has been the cause of many losses of ships, even though the ship may have been at rest and making no effort to move. Your own pages carry illustrations of just such action. There are many around the lakes who will have no difficulty in recalling such instances. Such fields cannot be forced so as to maintain a channel by any means at our command. All the ice breakers in the world could not maintain a working passage through Whitefish bay or the westerly end of Lake Superior or off Buffalo under the conditions existing there in April last. You will not fail to note that when a passage was once forced through the lower river it was maintained with little difficulty until the fields became loosened and began to move, resulting in forcing certain ships aground out of the channel as made. This because the conditions, first referred to, obtained. Damaging Effects on a Ship I have heretofore considered this subject in connection with the ice itself only, but there are other considerations which are equally important. The ship herself is one, the depth of water another. As to the former, the cargo ship is not designed to encounter ice, nor in fact any other floating or submerged obstacle. Attempting to force a passage with such a vessel is folly and the master who would attempt to do so either through closed ice fields or even heavy floating or drifting ice is not well equipped for his position. Underwriters long ago paid for their experience in this respect. Ships have foundered both on the lakes and at sea as a result of contact with both free and field ice. It is true «hat the opening just passed, although witnessing ice conditions probably as severe as any in the history of the lake marine, was free from such disaster, but that it was so is due most probably to the lessons of the past as well as to the pressure of the underwriters. The ship also furnishes another argument against any such proposition, namely, her propeller. While hull dam- age may be minimized by care it is practically impossible.