[138]

[in margin:] used King George Sound

Ed. Phil. Journal 1840 p. 353 &c

on casts of trees at Madeira - Refers to me.

[p. 353. Calcareous deposits, similar to that of Madeira, have been described by voyagers as occurring at the Cape of Good Hope, and in New Holland. Of the latter, the most recent account is given by Mr Darwin in the valuable and interesting volume recently published, containing the observations in Geology and Natural History, made in the expedition of H. M. Ship Beagle. In speaking of Van Diemen's land, he says:* "One day (March 1836) I accompanied Captain Fitzroy to Bald Head, the place mentioned by so many navigators, where some have imagined they saw coral, and others petrified trees, standing in the position in which they grew. According to our view, the rock was formed by the wind heaping up calcareous sand; during which process, branches and roots of trees, and land shells, are enclosed; the mass being afterwards consolidated by the percolation of rain-water. When the wood had decayed, lime was washed into the cylindrical cavities, and became hard. The weather is now wearing away the softer rock, and in consequence the casts of roots and branches project above the surface. Their resemblance to the stumps of a dead shrubbery was so exact, that, before touching them, we were sometimes at a loss to know which were composed of wood, and which of calcareous matter."

p. 356. Mr Darwin describes an analogous formation "considerably more than a mile square, covered with a forest of branching coral," p. 547.) produced in Keeling's Island, and by a similar cause, namely, the death of the coral over a large extent, from exposure to the sun, arising from change of level in the surface. There, however, the animal is that of the common coral, and the change of surface was produced by a gradual change of the surface of the ocean at the place.]

Consult other side

 

[138v]

The casts contain Ammonia

See whether the Superficial calcareous deposits of S. America contain animal matter.