Page:Popular Science Monthly Volume 7.djvu/498

482 spars are swayed up and sails bent, and the ship is again "all a taunto," and all are anxious once more to feel the long roll of the ocean. The open water is seen to the southward from the crow's-nest, but it is some distance off, and the ship is held fast in the wintry grasp of the ice. The month of June has come and gone, July is nearly at an end; if they are not shortly released, they will perhaps be doomed to spend another winter in that inhospitable and inclement region. During the preceding months those on board have not been idle, as a long line of ashes, sand, and rubbish of all descriptions, thinly sprinkled from the ship's bows in a long straight line to the southward, will testify. This has been done with the object of penetrating and rotting the ice, the dark color attracting the heat of the sun, so as to make a passage for the ship to pass through. This device has failed, and others must be resorted to to effect their liberation.

Blasting has been determined upon. Charges of three pounds, five pounds, and ten pounds of ordinary gunpowder will be prepared for use, in tin canisters, with Bickford's fuse. If, however, the new explosive "cotton gunpowder" should be the substance selected to carry out this object, a small charge of about two pounds is prepared, primed with its detonator, to which is attached a short length of Bickford's fuse. Operations are commenced from the open water and carried on toward the ship. A hole is made in the ice by means of a drill some distance from its edge, and the charge is lowered down through this until it reaches the water and is placed immediately under the ice. The fuse is ignited, a sharp explosion takes place, and the ice is shattered and rent in all directions. Men in boats, and others armed with boat-hooks and long poles, at once assail the fragments, removing them from the channel into the open water. These operations are repeated until a clear channel has been made, through which the ship is able to steam and thus effect her escape. The advantages which the "cotton gunpowder" has over ordinary black gunpowder are numerous. It is a much more powerful explosive, its proportionate strength to common powder being as eight to one, but its great merit is said to consist in its perfect safety. If put into the fire it will burn quietly, without any explosion, nor will it explode on concussion.

The practice of ice-blasting is not a new invention, and had been much resorted to by the various search expeditions. Their plan was simply to lower a glass bottle, or preserved meat tin, containing from two to four pounds of ordinary gunpowder below the ice, and explode it. The results were most satisfactory. Lieutenant Mecham tells us that during Captain Austin's expedition, in 1851, a blasting-party was employed for twelve days in detaching a floe from the eastern shore of Griffith Island. With 216 pounds of powder they cleared away a space 20,000 yards in length, and averaging 400 yards in breadth; this ice varied from three to five feet in thickness. The estimated weight of the ice removed was about 216,168 tons. The heaviest