The most easterly island is Frigate, the most southerly Platte; on the northern edge of the reef are Bird and Denis islands.
These are overlain, perhaps unconformably, by a great thickness of lavas and volcanic breccias (Pniel volcanic series, Beer Vley and Zeekoe Baard amygdaloids), and these in turn by the quartzites, grits and shales of the Black Reef series.
The Black Reef series of quartzites and conglomerates and dolomite form a narrow outcrop resting unconformably upon the last-mentioned system.
Deep. There are a few clear openings in the outer rampart which the reef presents to the ocean.
The Devonian system is well exposed in the Reef ton mining field.
The town, named after Johannes Rissik, then surveyor-general of the Transvaal, was founded in September 1886, the first buildings being erected on the part of the reef where are now the Ferreira and Wemmer mines.
It is approached by a deep channel through the coral reef which fringes the entire eastern side of the island.
Yes, and we flipped it at the rate of ten gallons the hour; and when the squall came (for it's squally off there by Patagonia), and all hands--visitors and all--were called to reef topsails, we were so top-heavy that we had to swing each other aloft in bowlines; and we ignorantly furled the skirts of our jackets into the sails, so that we hung there, reefed fast in the howling gale, a warning example to all drunken tars.
Often, as has been said, the atoll is divided into a number of islets, but in some smaller atolls the ring is complete, and the sea-water gains access beneath the surface of the reef to the lagoon within, where it is sometimes seen to spout up at the rise of the tide.
The black coral (Antipathes abies), formerly abundant in the Persian Gulf, and for which India is the chief market, has a wide distribution and grows to a considerable height and thickness in the tropical waters of the Great Barrier Reef of Australia.