118 



LORD HOWE ISLAND. 



saltic pebLlos and fragments rolled down from the North Hummock become 

 naturally cemented to the surface of the former. Denudation then setting 

 in, the pebbles afford to the immediately underlying Coral-sand rock a certain 

 amount of protection, and so a small pinnacle is formed, leaving the intruders 

 perched at the top. They resemble so many miniature towers, or roclies 

 perches, and are either isolated or arranged in curved lines and other fantastic 

 figures, when they give to the beach a very peculiar appearance. Pot-holes 

 are sometimes met with also. Veins and concretionary masses of calcite are 

 not uncommon, excellent examples of the latter being procurable in I'ern 

 and Peg-leg Q-ullies, behind Captain T. Nichols' house. 



I have succeeded, much to my surprise, in distinguishing two distinct periods 

 in this Coral-sand rock Series, separated by a well-marked unconformity. 

 The four best marked sections seen on the island by me are the following ; 

 three of them show the two series in sitti, the third only one. Taking the 

 last first, the following sequence is visible at Thompson's Point, from above 

 downwards : — 



1. Disintegrated and perhaps blown sand, intermingled with a little 



earthy matter, forming the soil, 1 foot. 



2. Thin stratum of red soil, containing semi-fossil Bulimus, 2 to 3 feet. 



3. Coral-rock, thinly laminated, forming the low bluff known as 



Thompson's Point, and believed to be dipping north, but the face 

 much obscured by fallen blocks and loose sand, 20 to 30 feet. 



This section is some fifty yards long, and may be taken as a typical one of the 

 Coral-sand rock when forming low sea cliffs. It will be referred to hereafter 

 in connection with the guano deposit. An equally good but higher section 

 is visible in the cliff to the north of the Deep Creek mouth. This, by 

 harometrieal measurement, is 100 feet above the sea-level at the highest 

 point of the cliff, but the bed No. 2 does not appear to be present. 



At the outlet of the Deep and Soldier's Creeks the lower division of the 

 Coral- sand rock runs into the Lagoon in long shelves and reefs, much broken 

 up by denudation, leaving isolated patches on the shore quite free of debris, 

 and, above all, clearly in situ. Here the unconformity is visible, the lower 

 stratification inclined, the upper horizontal, or nearly so, and the lamination 

 in both very thin. The inclination of the lower is 11° in a direction N. 75° 

 E., whilst the upper series when dipping at all is at about 3°, and towards 

 the north. 



The following sketch (PI. VII), in which these features are excel- 

 lently shown, is taken at the mouth of the Deep Creek,* and also exemplifies 

 the manner in which the long ledges of coral-rock run out, reef -like, into 

 the Lagoon. 



Prom the fact that only portions of the lower series are visible, and the 

 greater part of the upper has been removed by disintegration and marine 

 denudation it is impossible to estimate the thickness. An equally clear and 

 larger section is visible on the east coast in a conspicuous outlier of the Coral- 

 sand rock on the shore near the northern end of Middle Beach, and which has 

 been marked by Mr. H. T. "Wilkinson on his map as a volcanic rock. By far 

 the best, and most satisfactory section, however, is that along the south side 

 of Ned's Beach, exposed for about 200 yards, along the cliff of Wilkinson's 

 Promontory, above the beach. Here, whenever the face is clear of vegetation, 

 the junction of the two sets of beds is most distinctly to be seen. Three 

 observations of the lower inclined series gave the direction of the dip as "VV. 

 10° N., varying from 25° to 35°, the junction and unconformity being very 



*f rom a photograph by the Government Printer, taken during Mr. Cloete's cxpeilitiou. 



