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•'So varied, so imposing as these phenomena are, yet thej 

 appear to me ref errable to the same cause — a cause as simple 

 as it is energetic. In effect, the numerous minute shells which 

 multiply in these seas, and thrown up by millions upon the 

 shore, are subject to the twofold influence of an ardent sun 

 and a penetrating humidity. In losing a portion more or less 

 of their carbonic acid, they tend to approach to the state of 

 lime. This calcareous debris, pulverized by the action of the 

 waves, becomes mixed with the sand on the shore, and forms 

 with it a veritable calcareo-quartzose cement. This material 

 encrusts the various substances which are found on the shore — 

 shells, zoophytes, seaweeds, pebbles, all are agglutinated by it. 

 Transported by the winds this active matter is deposited upon 

 the neighbouring bushes — at first as a thin layer, later as a 

 solidified mass embracing the stem ; after this, the function of 

 nutrition is impaired, the plant languishes, and while still 

 living is in process of becoming petrified. On breaking the 

 branches of these kinds of lithophytes there is to be seen, if 

 the incrustation is recent, the ligneous tissue enveloped in a 

 solid case but without any remarkable alteration ; but as the 

 calcareous envelope augments, the wood is disorganised, and is 

 insensibly changed into a dry and blackish debris ; then the 

 interior of the tube preserves a diameter nearly equal to that 

 of the branch which has served it for a mould ; finally the tube 

 becomes filled with quartzose and calcareous particles, and 

 after the lapse of some years all is converted into a solid mass 

 of sandstone. I have frequently referred to those enormous 

 sand-dunes, which are raised like ramparts around the isles of 

 New Holland, and at various points on the mainland. They 

 exceed sometimes in height that of the tallest trees, and are 

 composed of a sand like that of the shore, susceptible as it is 

 of solidification, often the rock which supports them is of the 

 same origin. On the inner slope of these moving hills, there 

 grow various species of shrubs ; in such a position, sand driven 

 by the winds, or washed by the rain, accumulates at the foot of 

 the trees and insensibly overwhelms them. Then after long 

 periods of years have elapsed, the vegetable tissue in the trunk 

 is altered, after the same manner we have seen it destroy the 

 branch ; the substance of the ligneous layers, being much more 

 solid than that which occupies the intervals, is decomposed 

 less rapidly than the latter ; hence the concentric circles, which 

 give to these extraordinary incrustations the appearance of 

 true fossils, but on close observation it is easy to convince 

 oneself, that these apparently petrified trees are nothing else 

 than masses of more or less hard sandstone, which preserves 

 only the vegetable form which had served it for a mould." 

 That elevation of the land has taken place during the exist 



