Science & Progress.

Te Aroha News, Volume XI, Issue 1745, 26 June 1895, Page 2

Science & Progress.

CORAL FORMATIONS.

Beautiful Circular Beefe of Coral Rocb Sometimes Many Miles In Diameter. The low lying islands formed by the skeletons of the obral insects are some of the post wonderful productions of nature. JThey are only found in warm climates, between the twenty-eighth degrees of north and south latitude, and limestone pure and simple is the chief component of the coral reef, as it is of the mountains erupted from the depths of the sea. “The detritus of

~~ATOLL OBCOTALI^SrD.

corals, echlnodermata shells, reticularis and other living says a writer on this subject, “deposit not Only the salts of lime extracted from the ocean, but their own dead bodies, to form of the rook,” The coral Insect assumes purious and ele* Et forms, and the produces is 6 f or calcareous Aeyfßfc which la fixed upon a rooky base. go on these accretions become greater and greater, and at length rise above the water. The “atolls,” or oiroular coral reefs with an opening at one side, have been described by Professor Darwin. ‘*Who,” asKb the great naturalist, “would hot be struck with wonder and admiration on catching sight.for the first time of this vast ring of coral rock, often many miles in diameter? (Sometimes a low green island is seen beyond it, with a shorn of dazzling whiteness. Outside is the foaming surf of the ocean, and within it a broad expanse of tranquil water of pale green color and exquisite purity.?'. " . „ .. - 4 These “atolls” mqrk the situation of sunken islands, and the extension of them and the barrier reefs would seem to indicate a slow but deddeid sinking of thejtiottom of the -Indian and Other oceans, but the “reefs” tell us that the land to which they are attached has not become depressed ana may have become elevated. We may then conclude that rising and depression of riie land is taking plate in various deeans. ' Effect ot Alx and Ventilation on Coal. The effect of air and ventilation on *coal has been investigated by an English ohemist who reports the following results: > First—The danger of spontaneous firing Of coal in large lumps is very slight, but It is much greater with smaller coal and greater still with, dust, the increase of danger being due to the larger extent of sun£aoe exposed to the Mr in proportion to the mass of the coal. .Second—Air dried coal which contains more than 8 per cent of moisture is dangerous, but if it contains less the danger diminishes, the moisture contained being's measure of the absorbent power of the coal for air, and the more absorbent the coal the more dangerous. Third—The danger is somewhat increased by the presence of pyrites in large quantity. „ Fourth—Newly won coal should be shielded from the air as much to prevent the chance of rapid heating, and for the toe reason it is best not to stack it in large heaps, since these retain the heat. Fifth—All external sources of heat, sjach as steam pipes, boilers and hot flues in the neighborhood of the coal, add very greatly to the risk, spontaneous heating becoming vastly more rapid when it is assisted from without. Of course these conclusions have special relation to coal that is stored or shipped in cargoes. _