382 
Jukes on Australia. 
ranges of bills running in various directions, and the coast-line 
is indented by a multitude of bays, harbours, and channels, pene¬ 
trating into the land with much irregularity. To the difficulty 
thus arising from the external features of the country, is added 
that resulting from great complexity in its internal structure. The 
sedimentary and the igneous rocks are so interlaced and entangled 
one with the other, and their apparent relations at the surface so 
different in different localities, that nothing but a careful and 
minute survey, laid down on maps of a large scale, will ever be 
able thoroughly to elucidate them. ■* 
- A. The valley of the Derwent River. 
Along the S.W. side of the valley of the Derwent runs a bold 
range of flat-topped hills, of which one of the principal promon¬ 
tories is Mount Wellington, rising immediately behind Hobarton 
to a height of 4200 feet above the sea. The upper portion of this 
range is composed of massive greenstone, often forming rude 
columns of great size, frequently as much as ten feet in diameter. 
The lower slope of this range, and much of the country forming 
the opposite side of the valley, is composed of the paleeozoic 
rocks. These lie generally in a nearly horizontal position, and I 
believe abut horizontally against the greenstones ; but as I never 
found a clear section near the junction of the two, I cannot posi¬ 
tively say that they do not pass under them,—that the greenstones 
of the hill-tops are not a thick capping resting on the paleeozoic 
formation. In ascending Mount Wellington from Hobarton we 
first pass over a great thickness of white and yellow sandstones 
nearly horizontal; above these are shales and thin beds of lime¬ 
stone, likewise horizontal; over which again other sandstones are 
found. These rocks occur to a height of 2500 feet above the sea 
and apparently form a solid mass of that thickness at least. Above 
this point greenstone alone is to be seen, forming a mass 1700 
feet thick at least. Its total thickness depends of course, on the 
undecided question, of whether it be a capping to the paleeozoic 
rocks, or what I believe is much more probable, a solid mass with 
the sedimentary beds resting against its sides. 
Both the sandstones and limestones are quarried at several 
