1850.] MANTELL ON THE GEOLOGY OF NEW ZEALAND. 327 



some distance, and found the cliifs were composed of the blue ter- 

 tiary clay. The hills inland seemed to belong to the same age (clay- 

 slate) as the Pukehairi range at Waitaki. 



" At Waikouaiti, seventeen miles north of Otago, I found Mount 

 Watkins to belong to the same class. Dikes of columnar trap, the 

 columns at right angles to the sides of the veins, occur at Island Point, 

 the Bluff, and Brinn's Point. These dikes traverse a deposit of pale 

 buif-coloured sandy clay, distinctly stratified, and dipping about 40° 

 to the south-west. 



" In the little bight south of Island Point, in front of the native 

 Kaika, named Makuku or Waipipipaika, is the exposed part of the 

 so-called ' turbary deposit,' whence bones of the Moa have been ob- 

 tained in such numbers and perfection. This bed is about three feet 

 in depth, and not more than 100 yards in length, and lies imme- 

 diately on the tertiary blue clay ; it is visible only at low water. It 

 consists almost wholly of decayed vegetable matter, anr] its surface is 

 studded with the undisturbed roots of small trees, which appear to 

 have been burnt down to the ground at some remote period. It is a 

 light sandy elastic earth, of a blackish brown colour, emitting a strong 

 fetid odour when first collected. From the large quantity of flax 

 fibres {Phormium tenax) it contains, I conceive it was originally a 

 swamp *. 



*' At Blueskin and Purakaunui Bays, the primary country of Otago 

 begins, and boulders of serpentine of various shades of green are plen- 

 tifully scattered on the sand-hills around Purakaunui. These bays 

 afford an interesting illustration of the manner in which the harbours 

 are gradually filled up when they are situated in a curve of the coast, 

 and are exposed to a prevalent wind, and unprovided with a river ha- 

 ving a current of suflicient strength to keep open a serviceable channel. 

 Like Otago, each has a dry sand-spit running from its western nearly 

 to its eastern head, that has been formed by the joint action of the 

 sea and the land drainage : this constitutes a barrier, behind which 

 the detritus brought down by the inland streams from the mountains 

 tranquilly subsides, and eventually accumulates into a sand flat, 

 through which the water flows into the sea. Blueskin Bay lying in 

 the very bight, is the nearest advanced towards this state, to which 

 Purakaunui and other similarly situated bays are rapidly tending." 



I proceed to the examination of the specimens of rocks, minerals, 

 and organic remains, collected by my son during the journey, and 

 which are now in my possession. 



Rocks and Minerals. 



The collection contains between 200 and 300 specimens. With 

 the kind and able assistance of Prof. Tennant, I have carefully exa- 

 mined such as seemed likely to prove interesting in an economical 

 point of view ; but a very general notice will suffice for my present 

 purpose. They are chiefly pebbles and boulders from the line of 



* Further remarks on this deposit will be given in another part of this notice. 



