GEOLOGY. 



115 



investigation of this deposit. I am, however, inclined to the opinion that it 

 may he found concurrent with the Coral-sand rock, and that wherever sections 

 can be exposed, shoAving the junction of this with the volcanic series, then 

 the red clay will perhaps be met wiili also. So far as my observation went 

 it is unfossiliferous. 



3. Coral-sand roch Series. — The thin-bedded calcareous rocks included under 

 this name have been deposited either on low basaltic spurs or against the 

 flanks of hills of that nature. For all practical purposes it may be said to 

 form the narrow neck of land uniting the North Eidge with the southern 

 basaltic uplands, except Mount Lookout. Associated with younger deposits 

 it forms all the flat ground of this part of the island and some of the lower 

 hills, such as Wilkinson's Promontory, and extends, in an unbroken sv,-eep, 

 from the Old Settlement on the north to and inclusive of Moseley's Flat on 

 the south. Two other patches exist, one at the head of North Bay and the 

 other in the valley of the Deep Creek. On Mr. Wilkinson's map it is 

 represented at the former locality as forming two horns running up between 

 the hills, the westerly one forming the depression connecting North Bay 

 and the Grulch. I had no opportunity of following out the boundaries in 

 detail, but at the point where the boundary approaches the shore it is most 

 certainly erroneous. This is probably due to the faulty topography of the map, 

 already referred to. The hill-shading at this point represents the' slope of the 

 hill as descending to the shore, whereas in reality, immediately rising from 

 the latter is a low hill composed of Coral-sand rock, circumscribed on its other 

 three sides by shallow gullies, which from the boundary line between the Coral- 

 sand rock Series and the volcanic rocks forming the general mass of the North 

 Eidge. ^ On the low rise are situated two caves, excavated in the former. 

 Time did not permit of my following out the boundaries of the second patch, 

 that at the Deep Creek, except at its southern termination along the Fresh- 

 water Pool. Here the Coral-sand rock has, on the map, been carried up the 

 flanks of Mount Ledgbird, but I was quite unable to trace it beyond the 

 creek edge, which again appears to form the boundary. 



Mr. IT. T. Wilkinson describes the extent and boundaries of the deposit iji 

 these words : — " Following the coast line northerly from the western base of 

 Mount Ledgbird, the formation flanking the hills consists of blown sand as 

 far as a point 10 chains south of Eobbins' Point, where a basaltic spur from 

 the North Hummock comes down to the sea. From Eobbins' Point wo have 

 again the blown sand rock, which here forms the central rock of the island 

 between West Beach and Blenkinthorpe Bay. About a mile further north, 

 the west spur from Mount Lookout reaches to the beach, and immediately 

 beyond this the coral-sand rock forms the wdiole width of the island as far 

 as the north point of Ned's Beach on the cast, and Boat Pool on the west. 

 A small area of the sand rock again appears between North Bay and the 

 Gulch." 



The only eminences of any importance formed by this deposit are Thomp- 

 son's Pohit at the north end of the Lagoon, from 30 to 40 feet high ; the 

 cliff at Bobbins' on the west flank of North Hummock, about 30 feet ; the 

 cliff immediately to the north of the Deep Creek mouth, and above all 

 Wilkinson's Promontory. At each of these spots the Coral-sand rock may be 

 seen in excellent sections, when not obscured by its own debris ; these will be 

 described separately later. 



Over the surface of the lower flat grounds, back from tlie shore line, this 

 peculiar deposit is met with outcropping in small patches, and forming small 

 scarps along the crests of gentle slopes. Excellent examples of this feature 

 can be seen between the Old Settlement and Thompson's Point, around the 



