be increased, altogether (in a main breadth of 26 feet), about half an inch, or a quarter inch on either side. The depressed side, then, in its progress under water, as far as nine inches, will have expanded a quarter of an inch in width, and the raised side an equal quantity; and both sides will act on the contiguous ices with the mechanical force of a wedge of nine inches long and a quarter-inch at the thick end,—exhibiting, on the ordinary mode of calculating the power of the wedge, a gain of power for either side in the proportion of twice the length of the wedge,[O] or 18 inches, to a quarter inch, or as 72 to 1. The force acting on these wedges is that of the _weight_ of the men employed in sallying, when all are placed on one side of the deck right over the head or back of one of the wedges. In a whaler carrying fifty men, the weight available for this purpose, say that of forty-six or forty-eight of the crew, may be estimated at about three tons, one half of which only would act downward, the other half being expended in the resistance upward, of the opposite side. Hence the mechanical force hereby derived, as represented by these data, would appear to be that of two wedges of a power of seventy-two to one, each acted on by a weight of a ton and a half, that is, a force of the weight of 108 tons acting towards the separation of the ice and ship on each side. But only half the amount of these two forces, it will be obvious, comes effectively into operation; for the wedges, being on _opposite_ sides of the ship, act antagonistically, thus spending one-half of their power against each other, in the compressing of the opposite sides of the ship together. The force really in operation, then, serving to push off the ice from each side, or tending to separate the compressing masses of ice, will be equivalent to two weights of fifty-four or altogether to a weight of 108 tons. If there were no resistance either from the _friction_ of the ice on the ship’s sides, or from the _stability_ of the ship, the estimated mechanical force, for the case assumed, would no doubt take effect. The resistance from friction cannot, it is evident, be determined; but that of the ship’s stability might be easily represented. At the _commencement_ of the heeling position, however, the resistance from this source would be but trifling. In its actual influence, in ordinary cases, the stability might abstract, perhaps, a quarter or a third part from the entire force exerted, but still leaving a free action equivalent to the weight of seventy or eighty tons towards the separation of the ices, right and left. But the force ultimately brought into operation, after a sallying motion is once obtained, becomes still greater and more effective,—acting now and then, in the nature of concussion from the momentum of a portion of the ship’s weight, as thus may be illustrated:—