The weight of the crew, in the outset of the operation, being placed all on one side of the deck, and then suddenly transferred to the other, will, after the overcoming of the friction originally induced by the ice, cause the ship to heel, and, on the reversing of the action (by the men running back again across the deck) the direction of the heeling will be also reversed. The process being carried on with a strict attention to the adjustment of the moment of the running of the men (indicated by the word of command, “over”) to the time of change in the natural oscillations of the ship,—these oscillations (supposing the ice to be gradually receding) will increase to a maximum, whilst the incidental concussions of the ship’s sides against the contiguous ices will act as a “ram” on the wedge-like expansion of the width of her two broadsides. The additional force thus incidentally applied, it is evident, may be enormous. Hence the wonderful effects sometimes produced by my Father’s ingenious device of sallying,—effects not less important and striking when “clawing” to windward of masses of ice in boring, when, by the mere action of the wind on the sails the ship may have come to a stand, as when stuck fast betwixt equally compressing ices on both broadsides at once. The moment the sallying is perceived, the ship realises such relief from both pressure and friction, as to start a-head as if acted on by a magical power! It hardly requires, perhaps, to be explained, that our investigations of the operation of sallying in urging a path through encumbering ices, are, strictly, only illustrative. For the action of the ship’s side which we have considered as that of a regular straight wedge is, in reality, curvilinear, and, ordinarily, would be unusually thin at the apex, thus giving, at the commencement of the heeling movement, a much higher degree of mechanical power. The _extent_ of the compression on the ship’s sides, too, we could only consider in a particular case, such as one of thin ice, or ice touching the sides to no great depth. In case of compression from thick ice, having contact with the ship’s sides to a considerable depth, the resistance to the sallying would, of course, be much increased, and, by consequence, the operation less effective. It may just be added that the principle of sallying is evidently capable of still more powerful application by aiding the _weight_ of the men, in the first instance of movement, by auxiliary loads of guns, chains, casks, or other heavy bodies transferred to one side of the deck; or, in a still higher degree, by an auxiliary mechanical force derived from a “purchase” from the ship’s lowermast, or top-mast head, to an anchor fixed in a distant part of the ice on either side. An enormous power, it is evident, might be derived from a leverage of this kind, sufficient almost to compress or squeeze in the very timbers of the hull. * * * * *