V. Haast. — On the Geological Structure of the Southern Alps. 333 



The lowest beds on the western slope are gneiss-granites, overlaid by 

 rnica, chlorite and other metamorphic schists of similar origin. These 

 rocks are followed by clay-slates, semi-crystalline sandstones and felstones, 

 which in some instances form not only the summits of the central chain, 

 but even reach several miles across to its eastern slopes. They generally 

 contain quartz veins. Upon them reposes the great sandstone, conglome- 

 rate, clay-slate and shale formation, of which the greatest portion of the 

 Provincial District of Canterbury is composed, and which in many instances 

 can be followed for nearly seventy miles to the east. I have named this 

 extensive series of rocks the Mount Torlesse formation. On the eastern 

 side of the great anticlinal it forms a succession of huge folds, dipping 

 throughout at high angles, but these folds have been so much destroyed 

 during numberless ages, that at present their synclinals generally form the 

 summits of the mountains, while the deep broad valleys often run along 

 their anticlinals. Besides this folding a great deal of crumpling has taken 

 place, so that, although the general character of the arrangement has been 

 preserved, over a short space of ground the strata often strike and dip in 

 all directions of the compass. During my first journey to the head-waters 

 of the river Eangitata, in 1861, I discovered in the Clent Hills a series of 

 beds containing numerous impressions of plants, and some twelve miles dis- 

 tant in the Eangitata Valley at Mount Potts other beds containing fossil 

 shells and saurian bones. Professor F. McCoy, in Melbourne, to whom I 

 sent the collections made, for identification and description, informed me 

 that the plants were of Jurassic and the molluscs mostly brachiopods of 

 Upper Devonian or Lower Carboniferous age, both being identical with 

 exuviae found in the coal fields of New South Wales. However, judging 

 from the position and sequence of the strata in both localities, agreeing 

 with each other in a remarkable manner, though the Mount Potts beds are 

 of much greater thickness, I could not accept this conclusion, being con- 

 vinced that they were of the same age. Since that time it has been proved 

 by a number of experienced geologists, that the beds in New South Wales, 

 to which Professor McCoy alluded, are interstratified, and that consequently 

 they must be of the same age. 



Both palaeontologists and geologists have agreed that if there exist in 

 any geological horizon beds containing a marine fauna of an older together 

 with a terrestrial flora of a younger aspect, the former will more correctly 

 indicate the age of the beds. Thus, if the fossil shells of any given forma- 

 tion have a palaeozoic and the plants a mesozoic character, the beds in 

 which both occur have to be classified as palaeozoic. 



It would be foreign to the object of this paper were I to enter more fully 

 into this important question, but I may observe that both in India and 



