418 Transactions.—Geology. 
Maitai formation, for instance, are not generally so metamorphosed as to 
have destroyed the fossil remains which were almost sure to have occurred 
had these beds been laid down by the agency of water. 
The remaining specimens numbered 4, 8, 9, 10 still exhibit the structure 
of wood, but are completely converted into quartz, with a specific gravity 
of 2°6 to 2'8, and having grains of magnetic black sand, or thin lamine of 
. mica here and there between the growth-rings of the original wood, and in 
the caverns of the structure. These specimens may be picked up in thou- 
sands in our streets and in our gravel pits and cuttings, indeed scarcely a 
piece of quartz can be picked up which does not show woody structure. 
No. 5 is silicified wood resembling chert where the woody fibre is quite 
distinctly seen. No. 18 has woody fibre very fine and dense, but with true 
veins of crystalline quartz transverse to the fibre, just as if the wood in the 
lignite stage had, in shrinking, cracked and admitted the silicious water to 
deposit, amidst the chemical changes going on, true crystalline quartz. 
The water-worn condition of these pebbles must have resulted from a 
submergence, probably very slight, of the plains for some time. Indeed the 
lignite beds alternating with beds of clay and quartz gravel prove conclu- 
sively that this was the case, and that such alternations of level must have 
taken place, a great many times, during probably long periods, since we 
meet with thin seams of lignite, alternating with clay and gravel in the most 
natural way, for more than 200 feet in the bores that have been put down 
in the neighbourhood of Invercargill. These plains, then, on which we live 
and move to-day, but slightly elevated above the tide, have been so (only 
sometimes just as much below tide-mark as they are now above) for long 
periods, during whieh immense forests grew, decayed, and became quartz 
gravel, while for correspondingly long periods the tide washed over them, 
covering up with elay the deposits of timber to make lignite of them, and 
polishing the pebbles which had passed into a more advanced stage of 
change through the oxidizing of the carbon of these vegetable remains. 
This natural oxidizing of the carbon of the vegetable world at ordinary 
temperatures, or at temperatures considerably elevated under the surface, 
is probably a process which has not been comprehended in all its magnitude 
and importance. The small amount of carbon dioxide in the atmosphere 
(only about 3 in 10,000) has probably a misleading effect, leading us to con- 
clude that the process must be very insignificant when the product is so 
small, 
When we consider, however, that all the growing forests of the world, 
nay, the entire vegetable kingdom, derives its carbon principally from the 
carbon dioxide of the atmosphere, it will be comprehended what an enor- 
mous supply will be wanted. It will want little less than the oxidizing of 
