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Mesozoic rocks, and that the former were intruded through 
the latter and formed vast sheets, which, as overspreading 
caps, protected them in a large measure from the great denu- 
dation which undoubtedly occurred subsequently and of 
which there is the most abundant evidence throughout the 
plains and valleys lying within the limits of the Upper 
Paleozoic and Mesozoic Systems. 
Dr. Milligan and Chas. Gould also followed Strzelecki in 
this opinion, as all of these writers in their ideal sections 
picture the sedimentary formations as dipping continuously 
under the elevated greenstone mountains and tiers, against 
which they have already been describedas abutting more or less 
horizontally. Jukes, however, was doubtful of this relation- 
ship, and discussed the probability of certain greenstone 
masses being of older date than the sedimentary rocks. 
In the latter case we would have to assume that the narrow 
lineal strips of Carboniferous sedimentary rocks, as also the 
overlying coal measures, with their denuded and precipitous 
faces, flanking the main greenstone tiers and mountain ranges 
are, with the wasted members of the lower valleys and plains, 
only the mere remnant ofa once greatly extended sedimentary 
formation, which, by long-continued action of subzerial erosive 
agencies, were cut and wasted away in the formation of later 
deposits, and whatever elevation and dislocation has taken 
place locally subsequent to their deposition the earlier eruptive 
greenstone upon which they flank or rest may also have been 
similarly affected by them. The consequences of this 
assumption would therefore lead one to infer that the vertical 
faces at the higher levels abutting against the greenstone 
slopes are mainly the result of denudation rather than 
dislocation. Nodoubt, repeated general elevation movements 
in later times may account for some of the examples. At any 
rate, the greater elevation would intensify the erosive agencies. 
This assumption, althougii seriously affecting our prospects as 
regards the extension of our coal seams beneath the tiers in 
various parts of the island, has been demonstrated to be 
perfectly true so far as the greenstone and sedimentary rocks 
on the flanks of Mount Wellington are concerned. A section 
at the Cascades on the flank of Mount Wellington was 
practically tested by the Government during the previous 
year for the purpose of determining whether the Lower Coal 
measures as represented inthe Mersey Basin, existed beneath 
the fossiliferous marine mudstones and limestones which 
occur at the place named, and which appear to dip gently in 
the direction of Mount Wellington. After the diamond-drill 
penetrated through 600 feet of alternating layers of cal- 
careous mudstones and limestones, without discovering the 
existence of the lower coal measures, it pierced immediately. 
