260 PROCEEDINGS OF SECTION C. 
some hundreds of square miles in the South Esk basin, and 
elsewhere. Predominant among their contents are frag- 
mentary remains,of altered sandstones, shales, and lime- 
stones, which have attained the hardness of quartz through 
close contact with an igneous rock. Sometimes the evidence 
is more direct, as at Back River, near Buckland, where the 
coal-measures at the base of a lofty hill of massive diabase 
are seen dipping away from it at an angle of about 40°. 
The continuation of these beds now removed by denuda- 
tion, at the same angle of inclination, would carry them 
well over the summit of the diabase in precisely the same 
way that the sedimentary strata are reported to arch over 
the Mt. Hillers laccolite. 
Some mention must be made of an extensive area of which 
there is little accurate knowledge, and to which the laccolitic 
theory is generally supposed to be totally inapplicable. The 
structure of the elevated region of the interior, commonly 
called the Central Plateau, and often spoken of as if it were 
one continuous mass of greenstone, is in reality of a very 
complex character. It may be described in general terms 
as a tract of undulating country at an altitude of from 2000- 
to over 3000 feet, with a general southerly slope, bounded by 
diabase-capped mountains ranging from 3500 to more than 
5000 feet above sea-level, and traversed by lesser ridges of 
the same rock. The area of this elevated tract of country is, 
roughly speaking, about 3000 square miles. The outer 
ring of mountains viewed from the plain-country on the 
north and east appears to be continuous, but- the experience 
gained in flying visits to the Lake Country from the north, 
east, and south satisfied me long ago that there are numerous 
breaks in the diabase capping. Along the greater part of 
this outer ring there are thick-bedded remnants of the sedi- 
mentary rocks already mentioned as fringing mountains of 
this class, and at numerous points within it one comes upon 
outcroppings of denuded sandstones, &c., the lateral extent 
of which can only be guessed at. But for the protection 
afforded by this elevated outer ring to the greater part of 
the central upland area from the erosion which has excavated 
wide valleys and deep gorges outside it, the proof of the 
actual relations between the igneous and sedimentary rocks 
would not have been far to seek. 
Some old notes of a journey through the centre of this 
region from east to west, passing north of Lake Kcho, are 
not without points of interest in this connection. The 
undulating country between the rivers Shannon and Ouse, 
east of Lake Echo, consists chiefly of rocks of the Permo- 
Carboniferous series overlaid by basalt of various types, with 
