118 Coal- Seams of Van Dietnen's Land. 



These are questions, however, which can only he decided 

 hy a very minute and connected geological examination of 

 the whole area. 



In descending the valley of the Derwent from the first- 

 mentioned thin seam of coal, after passing over the edges of 

 the underlying sandstones for ahout three quarters of a mile, 

 another thin seam of coal may he detected cropping in the 

 hed of the stream. What the exact thickness of it is I could 

 not ascertain, as where it crops it has been washed away, 

 forming a pool in the river with an overhanging ledge of 

 sandstone rock. 



It did not appear to he more than a foot thick, and of 

 similar quality to the one above. 



This would be about fifty or sixty feet below the first 

 seam, the beds between being nearly all sandstone. 



A little lower down, where the river makes an elbow, and 

 nearly opposite the junction of the Plenty with the Derwent, 

 we again find the bed of the river, and both banks for a con- 

 siderable distance occupied by a solid mass of hard, dark, 

 augitic, columnar basalt : on the south bank it rises into 

 cliffs some thirty or forty feet high, through which the road 

 has been cut, exposing a good section of the igneous rocks 

 in various forms, and thus again cutting off the continuity 

 of the carboniferous series. From the above point for rather 

 more than four miles down the Derwent to the confluence 

 of the " Back River," there occur constant alternations of 

 greenstone dykes and carboniferous strata, the latter pre- 

 serving an almost uniform dip about W. 10 to 15 S. 5° to 8°. 



This would, supposing the igneous rocks to have been 

 erupted through the carboniferous beds without shifting 

 them, and the succession to be regular, give a total thick- 

 ness of carboniferous strata between the first-mentioned seam 

 of coal and the Black River of nearly nineteen-hundred feet, 



