132 TUE NATUEAL HISTOET EEVIEW. 



the author showed that the various silicates already mentioned were 

 directly deposited in waters in the midst of which the Eozoon 

 was still growing, or had only recently perished, and that they 

 penetrated, enclosed and preserved the structure of the organisms 

 precisely as carbonate of lime had done ; and he cites these and 

 other facts in support of his opinion that these silicated minerals 

 were formed, not by subsequent metamorphism in deeply buried 

 sediments, but by reactions going on at the earth's surface. 



December Itl, 1864. 



The following communications were read: — 1. " On the Geology 

 of Otago, New Zealand." By James Hector, M.D., E.G.S. In a 

 letter to Sir E. I. Murchison, K.C.B., E.RS., E.a.S.— The south- 

 western part of the province of Otago is composed of crystalline rocks 

 forming lofty and rugged mountains, and intersected by deeply cut 

 valleys which are occupied by arms of the sea on the w^est, and by the 

 great lakes on the east. These crystalline rocks comprise an ancient 

 contorted gneiss, and a newer (probably not very old) series of 

 hornblende- slate, gneiss, quartzite, &c. Eastwards they are suc- 

 ceeded by well bedded sandstones, shales, and porphyritic conglo- 

 merates, with greenstone-slates, &c., in patches, all probably of 

 Lower Mesozoic age. Then follow the great auriferous schistose 

 formations, which comprise an Upper, a Middle, and a Lower por- 

 tion ; and upon these occur a series of Tertiary deposits, the lowest 

 of which may, however, possibly be of Upper Mesozoic date, while 

 the upper, consisting of a Ereshwater and a Marine series, are uncon- 

 formable to it, and are decidedly much more recent. In describing 

 the auriferous formations, Dr. Hector stated that the quartz -veins 

 occurring in the schists were not often true " fissure-reefs'* (that is, 

 reefs that cut the strata nearly vertically and have a true back, or 

 wall, independent of the foliation-planes), but are merely concretionary 

 laminae that conform to the planes of foliation. The gold occurs 

 segregated in the interspaces of this contorted schist, but is rarely 

 found in situ. — Dr. Hector concluded with some remarks on the early 

 Tertiary volcanic rocks, observing that the period of their eruption 

 must have been one of upheaval, and that the great depth of the 

 valleys, which have been excavated by glacier-action since the close 

 of that period, proves that the elevation of the island, at least in the 

 mountain-region, must once have been enormously greater than it 

 now is. 



