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 laminae 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. 13 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 which immense forests grew, decayed, and became quartz 

 gravel, while for correspondingly long periods the tide washed over them, 

 covering up with clay 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 



