Page:Journal of the Royal Geographical Society of London, Volume 1 (2nd edition).djvu/250

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would result an appearance as if thls windward bulwark had really been erected by the ' instinctive foresight' of the animalcuhe. If the opinion we have thus hasarded be correct, it is evident that, in different situations, there will be coral rocks, exhibiting very different characters'; and thus, from the charts given of the coral islands which lie in the Indian and Chinese seas, in the regions of the six months' monsoons, it may be inferred that every side is equally advanced in formation. Chamizso says, that the larger species of coral insects, which form blocks measuring severel fathoms in thickness, seem to prefer the violent surf on the external edge of the reef; which, with the obstacles opposed to the continuation of their life in the middle of a broad reef, by the amassing of shells and fragments of coral, easily account for the outer edge of the reef first ap. proaching the surface; and the same circumstances must also contribute to the circular character of these reefs, or groups of reefs. Whether those izlands, which have greater length than breadth, are opposed in their greatest extent to the winds and waves, appears to depend on the size and arrangement of their submarine supports. The arguments of Quoy and Gaimard, who say that the species which form the most considerable banks, such as the Mea?drin? certain Cnryophyllen, nnd especially the Astre?e, require the influence of light to perfect them, and conse- ?edently cannot be developed at n depth of from ten to twelve hun- feet, are only applicable to those species; and if the species of the genus Astre-a ar'? alone capable of covering immense extents of surface, nnd do not commence their operations at a greater depth than twenty-five or thirty feet, why may not the branched madrepores, which do live at considerable depths, have formed the platform for their reception, just as we see the marine algae dis- tributed in different zones or depths of the sea * ? In the uncultivated tracts of our latitude, vegetation generally commences by the appearance of pulverulent lichens, which are succeeded by foliaceous plants of a more perfect organization, by mosses, and finally, varying with the soil nnd situation, by mono= cotyledonous or dicotyledonous plants, which gradually make their appearance; but the coral islands of the Pacific, not adapted to s?pport plants requiring a depth of soil, often first afford a basis to high trees provided with fi[wous roots, as the Pisonia, Cordia Sebastiana, Morinda citrifolia, and Pandanus odoratissimus, which, nt a distance, give to these small islands the form of a hill. The loose dry stones of the first ridge are penetrated by the hard roots .of the Tifano, which expands its branches into a tail, spread- ing tree, and is attended by the fragrant Suriana, and the sweet= scented Tournefortia, in the shelter of.whose foliage the Achy- ranthas and Lepidium seem to thrive the best. Beyond the first �Captain Beechey informed Mr. Lyell, that in Dueles Isla?d, W. l?ong. 1? � meert?ined tha? the eora? were growing a? the d?lp?h of one htmdr?d and fee?;,--Lyeli's Geology? p. 1?0. Digitized by GO0?[?