Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.2): between the years 1826 and 1836 : describing their examination of the southern shores of South America, and the Beagles's circumnavigation of the globe

1836. KEELING ISLANDS TIDE-GUAGE. 620 head, though the horizon was clear) — when a number of gan- nets flew past the ship towards the west. We steered directly after them, and early next morning (after making but little way during a fine niglit) saw the Keehngs right ahead, about sixteen miles distant. A long but broken line of cocoa-palm trees, and a heavy surf breaking upon a low white beach, nowhere rising many feet above the foaming water, was all we could discern till within five miles of the larger Keeling, (there are two distinct groups) and then we made out a number of low islets, no- where more than thirty feet above the sea, covered with palm-trees, and encircling a large shallow lagoon. We picked our way into Port Refuge (the only harbour), passing cautiously between patches of coral rock, clearly visible to an eye at the mast-head, and anchored in a safe, though not the best berth. An Englishman (Mr. Leisk) came on board, and, guided by him, we moved into a small but secure cove close to Direction Island. Many reasons had induced me to select this group of coral islets for such an examination as our time and means would admit of; and, as the tides were to be an object of especial attention in a spot so favourably situated for observing them, a tide-guage was immediately placed. Its construction was then new, and, being found to answer, I will describe it briefly. Two poles were fixed upright, one on shore (above high water mark, and sheltered from wind), the other in the sea beyond the surf at low water. A block was fastened to the top of each pole, and a piece of well-stretched log-line 'rove' through them.* One end of the line was attached to a board that floated on the water ; the other suspended a leaden weight, which tra- versed up and down the pole, on shore, as the float fell or rose with the tide. Simple as this contrivance was, and useful as we should have found it in many places where the surf or swell made it difilcult to measure tides at night, without using a boat, I never thought of it till after we left King George Sound. * A very small metal chain would be better, because a line, however stretched, will shrink after being wetted by rain, and give out again as it dries.