DIABASE OF TASMANIA. 2500 
capping of greenstone, supported on an outlying mass of the 
coal-measures, about six miles in length and two in breadth,” 
and his section represents this capping as presumably con- 
nected with a dyke traversing the underlying sedimentary 
rocks. Four years later, im a paper on the “ Geological 
Structure of the North-East Coast,’(°) he cites an instance 
in which the coal-measure sandstone is seen passing under 
the greenstone, with clear evidence of alteration at the 
point of contact, as controverting the views held on the 
subject by some other geologists. And he was in entire 
agreement with those who regarded all the greenstones of 
Eastern Tasmania, whether exposed at low levels or on 
mountain tops, as practically one and the same rock, and 
on or about the same geological horizon. 
I have myself verified most of the facts thus recorded, and 
the general conclusions have been supported by nearly all 
who have had opportunities of extended observation, includ- 
ing the Government Geologists, Messrs. A. Montgomery and 
W. H. Twelvetrees. Mr. R. M. Johnston, who stands with- 
out a rival in several fields of scientific research in Tas- 
mania, was at one time inclined to regard the Permo-Car- 
boniferous series as more recent than some of the masses of 
diabase exposed along the southern coast-line; but, in a note 
to a paper on this subject, read by him before the Royal 
Society in 1899,(7) he remarks that he had seen reason to 
alter that opinion. Professor T. W. E. David, in a paper 
on “ Volcanic Action in Eastern Australia,” (‘) read before 
this Association in 1893, refers to and supports some remarks 
which I made at the previous meeting, to the effect that “the 
greenstones of Hobart are intrusive masses, probably of the 
nature of laccolites, which are certainly of newer age than 
either the Permo-Carboniferous rocks of Hobart or than the 
Mesozoic coal-measures of New Town, Jerusalem, Fingal, 
&c.” 
So much for indirect evidence. On the sea-coast, where 
erosion still going on prevents the accumulation of talus, 
&e., that covers the zone of contact inland, there is ample 
proof of intrusion. Along the deeply- indented shores of 
D’Entrecasteaux Channel, Bruny Island, Tasman’s and 
Forestier’s Peninsulas, and the intervening country, there 
are very few headlands which are not composed of the 
typical diabase. This is often flanked or capped by masses 
(§) Transactions Royal Society, Tasmania, 1865, pp. 63-5. 
(7) Transactions Royal Society, Tasmania, 1899, p. 49. 
(*) Report of Australasian Association for the Advancement of 
Science, Vol. v., p. 403. 
