LANDING BY SWINGING DERRICK.
In some parts of the world, the operation of landing from a boat, or embarking from the quays or jetties built out into the sea, is rendered both difficult and dangerous by the great range imparted to the boat by the roll of the swell, which in the Eastern seas is at times very great. In such situations, it is a good plan to have a stout post set in the masonry, or in a hole made in the rock, and to the top of this post a swivel crutch, which holds the trunnions of a long projecting arm, like that of an Egyptian well lever, to the small end of which a rope and cross-bar are securely fastened. To the short, heavy end, several more ropes are attached, by which when the person to be landed has either grasped the cross-bar, or seated himself on it, the contrivance is at once raised aloft, and turned steadily but rapidly inward, when by easing off, the man is allowed to drop easily to his feet on solid ground. There used to be such a contrivance as this at St. Helena, by the aid of which we have often landed. The illustration on [p. 349] will serve to show how the apparatus is managed and constructed.
A barrel, stoutly lashed with rope, fitted with a seat, and cut away at the side, so as to admit of the traveller sitting in it, as in a chair, is used for ladies or invalids, who are slung in it at the end of the arm, and hauled in as above described.
Bridges of boats.
Sometimes it is necessary to construct bridges of boats; and these are often works of great magnitude, requiring a considerable amount of material, especially when an army with artillery and baggage waggons has to cross. Whether large or small, the method of proceeding must be nearly the same. First, a number of stout beams must be collected, sufficient to make a double line across the river, with their ends overlapping each other by more than the breadth of the boats that are to support them. The boats should be brought to the shore and moored a little above the site of the intended bridge. If anchors are procurable, they should be laid at regular intervals across the river; a buoy should be attached to the end of each cable, and a small line should lead from the farthest to each nearer one in succession, till they are all connected with the shore. A substantial frame of beams should be constructed at the edge of the bank, and a boat brought alongside it riding by the first cable, and secured by a temporary mooring to the shore. Two beams must be launched across her near the head and stern, and firmly lashed to the thwarts and stringers.
The boat must now be swung out to the full extent of the beams; the second cable must be laid hold of, and the first cast off and hauled to shore for the next boat, which is dropped down stream under the shore end of the beams, which are laid upon her gunwales and made fast there; while two others are pushed from the shore and fastened to her as the first pair were to the first boat. Intermediate beams, if requisite, can be laid, and planking lashed or pinned upon them so as to complete that part of the platform. Then other beams and planking, sufficient for a similar platform, should be brought on board, for the purpose of finishing the bridge when this pair of boats reaches the other shore. The outermost boat should now pick up the third cable, and pass the second to the inner one; while the first cable should be taken by a third boat, which will drop down between the others and the shore, to receive her portion of the platform; and so on in succession until the bridge, completed as it goes on, extends so nearly to the other shore that the loose material carried by the first pair of boats serves to complete the connection.
