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These were petrified trees, eleven being silicified, and from thirty to forty converted into coarsely-crystallised white calcareous spar. They were abruptly broken off, the upright stumps projecting a few feet above the ground. The trunks measured from three to five feet each in circumference. They stood a little way apart from each other, but the whole formed one group. Mr.
These were petrified trees, eleven being silicified, and from thirty to forty converted into coarsely-crystallized white calcareous spar. They were abruptly broken off, the upright stumps projecting a few feet above the ground. The trunks measured from three to five feet each in circumference. They stood a little way apart from each other, but the whole formed one group. Mr.
Eleven of these trees were silicified and well preserved; Mr. R. Brown has been so kind as to examine the wood when sliced and polished; he says it is coniferous, partaking of the characters of the Araucarian tribe, with some curious points of affinity with the Yew.
Tertiary formations of the Western Coast. Chonos and Chiloe groups, volcanic rocks of. Concepcion. Navidad. Coquimbo. Summary. Age of the tertiary formations. Lines of elevation. Silicified wood. Comparative ranges of the extinct and living mollusca on the West Coast of S. America. Climate of the tertiary period.
Thus, at a we see a macrospore, at b a fragment of the coat of a macrospore, at c another macrospore having a silicified nucleus, such as has been found in no other case, at d we have a transverse section of a vascular bundle, at e a longitudinal section of a rootlet traversed by another one, at f we have a transverse section of another rootlet, at g an almost entire portion of the vascular bundle of a root, and at h we see large pollen grains recalling those that we meet with in the silicified seeds from Saint Etienne.
The second point is, that the sandstone between Concepcion and Southern Chiloe is everywhere lignitiferous, and includes much silicified wood; whereas the formations in Northern Chile do not include beds of lignite or coal, and in place of the fragments of silicified wood there are silicified bones.
The various tufaceous and other beds at this northern end of Chiloe probably belong to about the same age with those near Castro, and they contain, as there, many fragments of black lignite and of silicified and pyritous wood, often embedded close together. Some of these spherical balls were encircled in the line of their equators, by a necklace-like row of smaller concretions.
This whole great pile is remarkable from the thousands of huge, embedded, silicified trunks of trees, one of which was eight feet long, and another eighteen feet in circumference: how marvellous it is, that every vessel in so thick a mass of wood should have been converted into silex! I brought home many specimens, and all of them, according to Mr. R. Brown, present a coniferous structure.
This elevated platform ends abruptly at d, in a line of perpendicular cliffs or bluffs, the base of which is continually undermined by the great river. Between the loam and the Tertiary formation there is usually a deposit of stratified sand and gravel, containing large fragments of silicified corals and the wreck of older Palaeozoic rocks.
Numerous facts, as in the case of geodes, and of cavities in silicified wood, in primary rocks, and in veins, show that crystallisation is much favoured by space.
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