156 



tend throughout the lower levels towards the Jordan and 

 Brighton. 



From the character of the beds and their fossil contents, 

 they may have formed part of the Richmond group. 



The following contains particulars of the section sunt by 

 Mr. Brock at Compton : — 



SECTION OF BROCK'S COAL SHAFT AT COMPTON, OLD BEACH. 



(a) Sandstone — 



1 Sand 8'9 



I Clay 6-0 



| Grey shale 12'0 



I Hard laminated blue and grey shales, 



(b) Y with impressions of Zeugophyllites 



elongatus, Phyllotlieca Hooker'i, and 



Thinnfeldia obtusifolia G'O 



| Red friable shales 5'0 



j Carbonaceous shales 0'3 



(c) Coal 2'0 



/ Carbonaceous shales 0'3 



(d). 



' Grey friable clay.. 

 With P. Hookeri.. 



40-3 



REMARKS ON THE LONGFORD COAL BASIN. 

 By Robt. M. Johnston, F.L.S. 



■The Norwich coal seams near Longford, opened out 

 by Mr. Mason and others, have only been discovered 

 recently, although the existence of the Mesozoic Coal Measure 

 Sandstones in the immediate neighbourhood — notably at 

 Hadspen — had long been known. 



The exact extent of this basin of coal has not yet been 

 determined. A glance at the geological sketch map, coloured 

 yellow, shows that nearly the whole of the plains north of 

 the Western Tiers, drained by the Tamar and its tributaries, 

 are superficially composed of sedimentary deposits belonging 

 to an ancient lake or water system of Palaeogene age (Lower 

 Tertiary), which deposits were minutely described by the 

 writer in 1873 and 1874, and termed the Launceston Tertiary 

 Basin.* 



These Tertiary rocks, with their accompanying intrusive 

 sheets of basalt, together with deposits of tuffs, overlie and 

 conceal the rocks of Mesozoic and Palaeozoic age, as in parts 

 of the Derwent Valley Basin. 



Rocks of Mesozoic and Upper Palaeozoic ago are to be 

 found everywhere bordering this ancient Tertiary Lake 

 Basin, and even near its centre, as at Hadspen, Corra Lynn, 



'Troc. Boy. Soc. Tas., 1873, pp. 39-47 ; 1874, pp. 53.62. 



