766 GEOLOGY OF THE NORTH-WEST COAST OF TASMANIA, 



with the trachydolerite of the lofty bluff of Circular Head 

 (Plate xxvii., fig 2) is concealed by sand dunes and drift, but 

 the relations of these two distinct types of volcanic rock appear 

 to be identical with those at Table Cape. 



Conclusion. 



The route or track described in this paper between the River 

 Mersey and Table Cape was not far distant from the line of the 

 present main road. From Table Cape to Circular Head it has 

 long since been abandoned, is practically unknown to travellers 

 along the coast, and in many places is impassable. 



The annexed plan and section (Plate xxviii.) constructed from 

 drawings made more than forty years ago on a horizontal scale of 

 one inch to the mile will sufficiently explain the relations between 

 the sedimentary and volcanic rocks along the coast-line described 

 in the Notes. The section, as regards the vertical scale, is 

 based on observation alone, the several altitudes having never 

 been surveyed, except that of the Circular Head bluff, which is 

 487 feet high. 



It seems probable that the great basaltic sheets rising gradually 

 from the coast had their origin in fissure-eruptions along anti- 

 clinal axes, the intervening folds being subsequently hollowed out 

 by the erosion of rivers of much greater magnitude than those of 

 the present day, or by glaciers slowly moving northward along the 

 lines of the present river-valleys. As to the geological age of 

 the ancient sediments which have been roughly described in the 

 Notes, there is no evidence forthcoming. With the exception of 

 the fossils of the Tertiary beds near Table Cape, and the fossil 

 wood from a breccia west of the River Leven, no evidence of any 

 trace of organic remains in the rocks of the North-West Coast has 

 yet been placed on record. In the absence of any positive 

 evidence on the subject it still seems safe to conclude that the 

 massive quartzite of Sisters Hills and Rocky Cape is the oldest 

 rock-formation of the series, and that it may be classed as 

 Archean, or at any rate Pre-Cambrian. 



In his admirable reports on the North-West Coast mineral 

 deposits Mr. Twelvetrees has suggested a probable alliance 



