GEOLOGY. 119 



apparent. The upper series is not, I think, quite horizontal, but has a very 

 gentle inclination eastward and northward. This excellent section brings 

 prominently forward two important points connected with the Coral-sand rock 

 deposit, viz., the constantly changing dip of the lower series, and the approxi- 

 mate greater thickness of the upper. The direction of the dip is here quite 

 different from that observed on the western side of the island, and the steady 

 continuance along such an extent as here shown must be looked upon as 

 exceptional. 



From the fact that the Coral-sand rock was deposited on the denuded 

 flanks and perhaps summits of pre-existing hills, it necessarily follows 

 that its thickness must be very variable. I am not aware that any 

 excavation has been sunk to prove it, but Captain T. Nichols estimates 

 that, in the neighbourhood of Fern and Peg-leg Grullies, the Coral- 

 sand rock attains a thickness of at least 80 feet. By rough barometrical 

 measurement, the height of the plateau running back from Wilkinson's 

 Promontory was found to be perhaps 250 feet. I traversed this plateau from 

 end to end, and crossed its flanks at various points, and was unable to detect 

 any other form of rock than the Coral-sand rock, and further I believe this to be 

 the greatest altitude to which the latter extends. Allowing the junction of 

 the two series, at Ned's Beach, to be between 30 and 50 feet above high- 

 water mark (say 40 feet), it is not more, we have for the thickness of the 

 upper beds, no less than 200 feet. 



In a preliminary investigation extending over but a short time, many 

 difficulties present themselves, which could only be solved by a regular 

 detailed survey. On this ground some of the points now brought forward, 

 will require confirmation. But it may be accepted with confidence that the 

 Coral-sand rock was deposited on the flanks of basaltic islands, of much greater 

 extent than now existing. I believe a break in this deposition occurred, 

 whether partially or wholly so, it is difficult to say, but probably the latter. 

 An unconformity however most certainly exists. Evidence of this, as before 

 stated, is only visible at a few spots, what with the dense vegetation generally 

 clothing the sea faces, and the tumbled condition of the sections. I was 

 much puzzled at first by the everchanging dip, sometimes highly inclined, 

 sometimes horizontal, just as the upper or lower series happened to be within 

 view. By an inspection, however, of the sections described, this peculiarity 

 was explained. 



On a low rise, at the head of North Bay small caves are weathered out of 

 the Coral-sand rock. One of these is about forty-five yards long by from 

 twenty-five to thirty yards wide, and some sixteen feet high. The descent, 

 although through an irregular half -choked aperture, is not difficult, and the 

 roof is partially covered with impure stalactites. The second cave had become 

 so much filled by falls that it was not worth or capable of investigation. 



The Coral-sand rock is the chief fossiliferous deposit on the island. It 

 has yielded the remains of the interesting reptile, named by Professor Sir R. 

 Owen, F.R.S., &c, Meiolania, eggs of turtles, bird-bones, and recent species 

 of both land and marine shells. 



Mr. Fitzgerald states that " curious pipes pass through the stratification, 

 which may have been formed by stems of palms ; they are hollow at the 

 centre, and the particles of coral are solidified at the circumference, so that 

 at some places they project like short chimney-pots."* Examples of such 

 cylindrical tubes did not come under my notice, but no doubt the descrip- 

 tion is accurate. The impressions and moulds of trees had long been known 

 in similar deposits, and in many countries. Darwin describes them at King 



* Hill's Lord Howe I4and loc. cii. p. 45. 



