On the Structure and Distribution of Coral Reefs: Also Geological Observations on the Volcanic Islands and Parts of South America Visited During the Voyage of H.M.S. Beagle |
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accumulation albite andesitic angle appears Archipelago atolls augite banks barrier-reefs basaltic beds calcareous Captain Moresby Chagos Chagos Bank chart Chile clay-slate claystone cleavage cliffs coast coloured compact composed consists Coquimbo coral coral-reefs coral-rock Cordillera crater crystalline crystals d'Orbig d'Orbigny denudation deposit depth described dikes distance earthy elevation embedded erupted escarpment fathoms feet in height feet in thickness feldspar feldspathic foliation formed fragments fringed geological gneiss granite gravel hills horizontal hornblende hundred feet inclined islands Isld islets lagoon laminated land lava layers lime Maldiva mass miles mountains nearly northern numerous observed origin Pampean parallel Patagonia pebbles plain porphyritic conglomerate porphyry probably quartz range reef remarkable resemble ridge rocks round sand sandstone schists sediment seen shells shores side slope southern species specimens strata stratified streams structure submarine subsidence surface terraces tertiary trachyte tuff upper upraised valley veins volcanic Voyage
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Page 159 - s lectures on Geology and Zoology, but they were incredibly dull The sole effect they produced on me was the determination never as long as I lived to read a book on Geology, or in any way to study the science.
Page 4 - No other work of mine was begun in so deductive a spirit as this, for the whole theory was thought out on the west coast of South America, before I had seen a true coral reef. I had therefore only to verify and extend my views by a careful examination of living reefs.
Page 9 - If I am wrong, the sooner I am knocked on the head and annihilated so much the better. It still seems to me a marvellous thing that there should not have been much, and long-continued, subsidence in the beds of the great oceans.
Page 345 - The gypseous beds are very remarkable, from abounding with, so as sometimes to be almost composed of, irregular concretions, from the size of an egg to that of a man's head, of very hard, compact, heavy gypsum, in the form of anhydrite. This gypsum contains some foreign particles of stone ; it is stained, judging from its action with borax, with iron, and it exhales a strong aluminous odour. The surfaces of the concretions are 1 ' Voyage,
Page 261 - These calcareous, branching bodies, appear to have been formed by fine calcareous matter being washed into the casts or cavities, left by the decay of branches and roots of thickets, buried under drifted sand. The whole surface of the hill is now undergoing disintegration, and hence the casts, which are compact and hard, are left projecting. In calcareous sand at the Cape of Good...
Page 5 - I had during the two previous years been incessantly attending to the effects on the shores of South America of the intermittent elevation of the land, together with denudation and the deposition of sediment. This necessarily led me to reflect much on the effects of subsidence, and it was easy to replace in imagination the continued deposition of sediment by the upward growth of corals. To do this was to form my theory of the formation of barrier-reefs and atolls.
Page 4 - To Charles Lyell, Esq., FRS, this second edition is dedicated with grateful pleasure — as an acknowledgment that the chief part of whatever scientific merit this Journal and the other works of the Author may possess, has been derived from studying the well-known and admirable
Page 254 - To descend into some of these valleys, it is necessary to go round twenty miles; and into others, the surveyors have only lately penetrated, and the colonists have not yet been able to drive in their cattle. But the most remarkable feature in their structure is, that although several miles wide at their heads, they generally contract towards their mouths to such a degree as to become impassable.
Page 190 - This structure is very simply explained, if we suppose a mass of viscid, scoriaceous matter, to be projected with a rapid, rotatory motion through the air ; for whilst the external crust, from cooling, became solidified (in the state we now see it), the centrifugal force, by relieving the pressure in the interior parts of the bomb, would allow the heated vapours to expand their cells ; but these being driven by the same force against the already-hardened crust, would become, the nearer they were...
Page 159 - The science of Geology is enormously indebted to Lyell— more so, as I believe, than to any other man who ever lived.