INCRUSTATIONS ON PLANTS. 
309 
Similar bodies have been found by Vancouver, Flinders, and 
Peron * on the shores of New Holland, at considerable elevations. 
The two first-named travellers considered them all as coral, and as 
proofs of the land having been lately withdrawn from the dominion of 
the waters. The last has described two kinds of substances ; the one 
he considers coral, and the other as incrustations on vegetables. Of the 
latter he gives ample descriptions, and explains the formation in a 
manner which appears to be satisfactory, and to apply to the sub- 
stances found by Captain Maxwell near Simon’s Town. He supposes 
that the shells cast on the shore and submitted to the double influence 
of an ardent sun and penetrating moisture, undergo a species of 
chemical decomposition; and having lost a portion of their carbonic 
acid, approach to the state of the lime used in some calcareous 
cements, and in this state unite into a compost with quartz sand, 
and form incrustations on the surfaces of plants. In another pas- 
sage he illustrates the steps of the process by a description of the 
appearances of several specimens. “ In breaking,” he remarks, “ the 
branches of these species of Lythophytes, when the incrustation is 
recent, we observe the woody texture contained in a solid case, and 
without any remarkable alteration ; but in proportion as the calcareous 
envelope increases, the wood becomes disorganized, and changes in- 
sensibly into a dry and black powder.” From this state he supposes 
the centre gradually to increase in solidity till the whole mass 
becomes a mere sandstone, and nothing but an arborescent form 
indicates the ancient state of vegetation, -j- 
* Vancouvei’’s Voyages. Vol. i. p. 48 et 49. Voyage to Terra Australis, by Captain 
Flinders. Vol. i. p. 63. Voyages aux Terres Australes. Vol. ii. p. 169. 
f Les nombreux coquillages qui pullulent dans ces mers, rejetes par millions sur la 
greve, sounds a la double influence d’un soleil ardent et d’une humidite penetrante, ne 
tardent pas a subir une espece de decomposition chimique dans leur substance. En 
perdant une portion plus ou moins considerable de leur acide carbonique, ils tendent a 
se rapprocher de cet etat oil est la cliaux quand nous l’employons pour servir de base 
a nos cimens ; et ce n’est pas en ce seul point quq les procedes de la nature se rapprochent 
