Geological Specimens from Tasmania. AQ7 
Query.—Have the so-called striped agates and flints origi- 
nally been woody matter, and by the absorption of water 
charged with molecules of mineral matter, say silex, become 
crystallized minerals ? 
No. 83—the Fossil Tree at Macquarie Plains—ig 9 
very interesting fact, and opens a wide field for geological 
and mineralogical speculation. The specimens you haye 
sent me show no appearance of the action of fire nor vitrifi- 
cation, or at least no more than opalized wood does; and 
when you crumble the fibres of the tree with your fingers, 
which you easily can do, it is reduced to a powder of silex— 
and when viewed through a magnifying-glass it exhibits, 
when only half reduced to a powder, rather a high state of 
erystallization, in a needle-shape form, which is nearly trans- 
parent. 
The darker part of the graining of the wood, which I con- 
sider to have been the resinous part, is much harder, and 
requires a light hammer to break it; and when broken into 
small fragments, it resembles in appearance gum-arabic. It 
appears to me that this fossil tree has never come into direct 
contact with the real fire of the volcano, but has been ovor- 
whelmed or covered by what the volcano has discharged ; 
and at the same time been placed in a favourable position 
for absorbing moisture, mixed with mineral matter, and. 
warmth through the cracks or fissures of the strata in the 
neighbourhood—and so gradually becoming mineralized and 
crystallized, at the same time preserving the ramification of 
the structure of the tree, almost as perfect as when a living 
tree. 
The rock in which it has been imbedded resembles much 
in appearance the structure and colour of porcelain jasper, 
but does not, like that mineral, scratch glass; but as regards 
hardness under the knife, they are very much the same, and 
