Sunken reef

“ The footsteps of a man were seen on shore, perhaps one of the Harrington's Lascars as the foot was measured and found very small. The shores of this island are bold rock and some dangerous reefs lie off it, one of which (a sunken one) we did not escape by 10 yards...Lady Nelson's Reef is east-south-east and west-north-west distance about 30 miles in Latitude 40 degrees 20 minutes 30 seconds south and Longitude by Time-keeper 145 degrees 40 minutes 53 seconds, it has many sandy bights in it where I would not scruple to anchor in south-south-west, south-east and east winds. ”

“ All those colours of shoaling sand and coral beds are only visible when the water is rippled. A few stones, mere specks here and there above the glassy surface alone shew the presence of a reef on which no swell is breaking.
Calm is thus more dangerous to a steamer than storm, for should she approach the reef areas before picking up the beacons and lighthouse that mark the entrances to Port Sudan and Suakin, she runs great risk of striking an invisible reef. Sailing vessels are safe, as whenever they are under way the water is rippled and the reefs easily seen. ”

“ Owing to the existence of the barrier reefs the approach to Suakin is down a 30-mile passage parallel to the coast, and from two to five miles wide. The shore becomes very low, and the fringing-reef wider than near Port Sudan, so that the distinction between sea and shore would be almost untraceable but for the presence of those salt-loving plants which grow everywhere along high water-mark. ”

“ The barrier reef, in fact, constituted a magnificent natural breakwater, upon which the surf eternally broke in a loud, sullen roar of everlasting thunder, while inside it the water was smooth as a mill pond, shoaling very gradually from the reef to the shore of the island, which consisted of a narrow beach of dazzling white sand, bordered by a fringe of thousands of cocoa-nut palms, the long, plume-like branches of which swayed gently in the soft, warm morning breeze. ”

“ This reef was discovered by Captain Hunter in May, 1791, two days after he had passed Stewart's Island (Sikayana) , and is doubly dangerous in a climate where the sea rarely runs so high as to make it easily observed by the surf breaking over it. ”

“ I thought, as I sprang on deck.
The wind was increasing, the foam-topped seas rolled in quick succession towards us, the sky to windward looked threatening in the extreme; that terrible wall of foam loomed higher through the gloom of night. Still, as long as the schooner’s head could be kept turned away from the reef, we might hope to claw off from it. The chart had shown us that a reef existed, but its form was indistinctly marked. ”

“ As in the Red Sea the level rarely alters by more than a foot once in the twenty-four hours, and often the rise or fall is much less, the action of tidal currents is at a minimum, yet even so they produce well-marked effects.
[117] Barrier reefs may be formed from fringing reefs by the enlargement of the boat channel, while the reef is extending seawards.
The island of Zanzibar, 60 miles long by 20 wide, and 20 miles from the mainland of Africa, seems to be a part of the East African barrier system, and it certainly was separated from the mainland by the destruction of the intervening land ”

“ Presently we caught on one; and dreading a capsize, we launched the boats at once; for there was not a point of the reef above water for miles, and no swimmer could have reached dry land in such a current. After a few anxious moments, the schooner swung free, and we dropped the anchor in a sort of pool. All the afternoon we were engaged in kedging out into the channel; and finally, after enormous labour, we got into deep water, where we anchored for the night.
The beauty of these coral reefs is something indescribable; nowhere else, either on sea or land, are such colours to be seen. ”

“ These ever-growing reefs would surround the whole coast were it not for the fresh water that oozes out from the land and prevents the coral from growing at certain points, thus keeping open narrow passages through the reef, or wider stretches along the coast free from rocks. These basins form good anchorages for small craft, as the swell of the open sea cannot cross the reef; only the entrances are often crooked and hard to find. ”

“ High, precipitous, perpendicular, level, and dotted with farm-houses, this singular bit of land stretches several miles out southward to sea, bordered with a rocky beach, and tapered off into the wide ocean with Duxbury Reef—a dangerous rocky reef, curving down to the southward and almost always white with foam, save when the sea is calm, and then the great lazy green waves eddy noiselessly over the half-hidden rocks, or slip like oil over the dreadful dangers which they hide. ”

“ The appearance of the reef made it probable that they were in the neighbourhood of other reefs and low coral islands, and they anxiously waited for daylight in anticipation of discovering the particular island of which they were in search. Standing to the south they cleared the reef, and once more, having shortened sail, they stood on their course.
The sun was just rising, a vast globe of fire, out of the purple ocean, when Elton, who had gone aloft, shouted, “Land! land! A low island, with palm-trees on it!” ”

“ These reefs, however, vary in construction; some are called encircling reefs, when they appear at a distance from the shore, and a lagoon intervenes; others are called fringing reefs, which are joined to the land, and extend out from it without any lagoon. Others are denominated lagoon islands, when the reef itself, raised above the surface of the ocean, forms the land generally in a circular shape, and surrounds a lake or lagoon, which has sometimes a passage to the sea, and at others is completely closed. ”

“ The barrier reef—that singular breakwater that makes so much of the circuit of Pacific islands—is carried far to sea at Matautu and Mulinuu; inside of these two horns it runs sharply landward, and between them it is burst or dissolved by the fresh water. The shape of the enclosed anchorage may be compared to a high-shouldered jar or bottle with a funnel mouth. Its sides are almost everywhere of coral; for the reef not only bounds it to seaward and forms the neck and mouth, but skirting about the beach, it forms the bottom also. ”

“ At New Caledonia (Plate II., Figure 5.) the barrier-reefs extend for 150 miles on each side of the submarine prolongation of the island; and at their northern extremity they appear broken up and converted into a vast atoll-formed reef, supporting a few low coral-islets: we may imagine that we here see the effects of subsidence actually in progress, the water always encroaching on the northern end of the island, towards which the mountains slope down, and the reefs steadily building up their massive fabrics in the lines of their ancient growth. ”

“ About a mile more or less off shore, there is as a rule a rocky reef, on which the breakers may be seen to dash violently in many places, the depth above the reef being in several places, 1, 11⁄2 and even 2 fathom, so that pinnaces and boats may get over it for the purpose of landing, there being deeper water close inshore, but all of it with a rocky, sharp coral-bottom, so that it is difficult to land there, and much harder still to keep a pinnace at anchor with a drag ”

“ At this hour of low water the reef was showing its teeth and snarling with surf. At high tide it would be hidden, and a perfect snare of ships. According to the map, the wreck lay in some eight fathoms of water, midway of the outer crescent of the reef. Behind the reef, where the latter might serve them as a partial shelter from the sweep of the seas if a northeaster should blow up, they found tolerable anchorage for the tug. For the preliminary soundings, and for the diving operations, of course, Jan planned to use the launch. ”

“ Since Raiatea is thirty miles in circumference, and Tahaa fifteen miles, some idea may be gained of the magnitude of the reef that encloses them. Between them and the reef stretches from one to two miles of water, forming a beautiful lagoon. The huge Pacific seas, extending in unbroken lines sometimes a mile or half as much again in length, hurl themselves upon the reef, overtowering and falling upon it with tremendous crashes, and yet the fragile coral structure withstands the shock and protects the land. Outside lies destruction to the mightiest ship afloat. ”

“ Pearl-shell is collected on the reefs, but not as yet in sufficient quantities to establish a lucrative industry. In this respect the island is not so fortunate as Alphonse, for there are no sheltered rock-pools in which the shell can be collected by swimming-divers without danger from the sharks; the sea everywhere flowing in over the outer edge of the broad fringing reef, and the great reef to the southward only drying in patches at low tide. ”

“ Outside the reef there is no anchorage ground, as no cable could fathom the depth. Inside, the water is smooth and beautifully clear, but no ship of any size can pass through the reef. There are several passages for canoes and boats, and one for a vessel of forty-five tons. This is, however, a very great advantage to the inhabitants in a social point of view, as it prevents the establishment of a seaport town in their island, while, at the same time, they can enjoy intercourse with the rest of the world. ”

“ As we bore rapidly down upon the reef, the passage through it gradually assumed its true proportion of width, and I saw that there was ample room to allow of the passage, not only of the brig, but of a couple of line-of-battle ships abreast. The island had the appearance of being simply the topmost ridge of a mountain rising with a tolerably even continuous slope from the bottom of the sea; and the barrier reef was merely an excrescence or wall of coral built on to one side of it, and founded at a depth of ten fathoms below the surface of the ocean, as our lead presently told us. ”

“ Owing to the practical absence of tide in the Red Sea the boat channels of the fringing reef are discontinuous, so that at intervals the canoe men must wait for favourable weather and put out to the open sea. In Zanzibar, e.g., one can travel the whole 60 miles of the east coast within the reef but for the crossing of one bay, except at lowest spring tides. ”

“ The shore itself is extremely low and sandstone hills are absent. The area marked Shubuk, south of Suakin, shewn on the map enclosed by a thin semicircular line on the north and east sides and by the land on the [151] west and south, has a very remarkable structure. An area of 100 square miles is enclosed by a regular and unbroken reef, indicated by the above curved line, the space within being a most intricate maze of reefs with comparatively deep canal-like passages between them. In the south are broader passages and some islets of elevated coral. ”

“ It was fortunate to find anything like a second suit on board a Mexican craft of that size at all. As it is, we have foresail, mainsail, and jib, and with that canvas I think we might beat the schooner down to Key West in the course of a day and a night. If I dared to venture outside of the reef, it might be done sooner even, for they tell me there is a four-knot current sometimes in that track; but I do not like to venture outside, so short-handed. The current inside must serve our turn, and we shall get smooth water by keeping under the lee of the rocks. ”

“ The Raiatea barrier-reef, about a mile offshore, is no more than a low dyke of coral, half awash and breaking the landward run of the swell. By night, when the torches flicker and flare, and mighty combers, bursting on the outer edge, come foaming waist-deep across the jagged rock, the reef is an eerie place, not without dangers of its own. Under cover of darkness, strange monsters have been known to crawl up from the depths on the seaward side—the huge decapods on which the sperm whale feeds, and nameless creatures of which the natives speak with whispered dread. ”

“ The plain is formed of gravel from the high hills, its yellow border seawards being coral limestone, and the islands also. In the sea are numerous reefs, here of very intricate plan, lines of white breakers separating the deep blue black water from large areas of green and brown shoals in waveless lagoons. There are deep channels between these reefs and the shore, which is itself fringed by a shallow reef with its edge at low water level but bearing perhaps one or two fathoms of water on its surface within. ”

“ In those low latitudes the day comes quickly, and we had not occupied our lofty perch many minutes when up leapt the sun, flashing his golden beams over the dark expanse spread out around us, and we saw, to our dismay, that we occupied a small basin—one of many such—situated almost in the exact centre of a vast reef, stretching over a distance which we roughly estimated at thirty miles from north to south, and perhaps twenty miles from east to west. The salt water that had been hove up with the reef had by this time all run off, leaving the dark, weed-covered rock fully exposed to view. ”

“ The Titania moored in nine fathoms, with her main anchor laid out in the direction of the reef, at about two hundred and fifty yards from the sandy shore of a small bay. At its northern extremity the bold headland of the bay almost touched the reef, there being a passage of about fifty yards leading to the next section of the lagoon.
"A south-easter is the only wind likely to trouble us," observed Villiers. "The reef will keep a lot of the sea down, but it's so low that there's bound to be a fairly-heavy tumble."
"What sort of bottom have we?" asked Harborough. ”