106 



diminution of 168 feet, from which circumstance I am 

 of opinion that the intermediate rock of the eastern 

 sections is coterminous with the chalk rock of the western 

 ones ; both rocks are made up of the same material, though 

 differing in colour and amount and degree of fineness of the 

 earthy constituent. In other words, they haVe been derived 

 from the one source ; but the distribution of the debris has 

 been regulated in accordance with its different degrees of fine- 

 ness and distance of transport. The white chalky rock occupies 

 the deeper parts of the granite basin ; whereas the shore 

 deposits are sands and crystallised limestones, as is proved by 

 the sections about Pidinga. (See below.) 



The Cbystalline Limestone is for the most part fine 

 grained, and varies in colour from white to grey, brown, and 

 pinkish. It is brown on the Bunda cliffs, but on the escarp- 

 ment of the Hampden Range it is externally hoary, which 

 produces a pleasing contrast with the dark foliage of the scrub 

 clothing the slopes through which the white surface of the 

 rock glimmers. As seen on the coast this band is deeply 

 fissured and cavernous, and is further divided by joints, which 

 cause it to separate into huge cubical blocks. 



It occupies the topmost position of the Older Tertiaries 

 throughout the whole extent of the Bunda cliffs, and it crowns 

 the escarpment of the Hampton Range ; it is seen in the same 

 position in the wells and caverns between the Bight and Mai- 

 lable, and, so far as is known, makes the surface of the ground 

 over the whole arid portion of the Bunda Plateau ; indeed, it 

 is mainly to this circumstance that the Plateau owes its 

 peculiar characters. It abuts against, and occupies the depres- 

 sions in, the granite and metamorphic rocks about Pidinga ; 

 where, resting on gneiss, its base is conglomeratic, but where 

 mica slate is the underlying rock a clay intervenes. A section 

 showing the junction of the latter is as follows, taken at the 

 low escarpment bounding the Pidinga rock basin, at about 

 half a mile south of the Talacoutra rock hole. (See horizontal 

 section, pi. iv., fig 1.) 



feet. 

 "Whitish yellow shelly limestone, with cast of fossils... 3 

 Yellow clay... ... ... ... ... ... ... 5 



Red and purplish clay, decomposed mica slate, in situ 5 



At distances varying from 18 to 28 miles north from Colona 

 towards Pidinga, three wells have been sunk in older Ter- 

 tiary limestone interspersed with sand. The section in the one 

 18 miles from Colona is as follows: — 



