BY RB. M. JOHNSTON, F.L.S. 139 
might reconcile my judgment with the apparently strong 
opposing evidences presented by the extent, mass, positions, 
and continuous relationship of the greenstone rocks under- 
lying the mudstones between Blackman’s Bay and Adventure 
Bay in South-Eastern Tasmania. Mr. Montgomery’s and 
Mr. David’s reasonings, I confess, have also had much weight 
in disposing my mind to contemplate a result of this kind. 
Let me be just to myself, however, by quoting my earlier 
remarks on this important question. In commenting upon 
the pros and cons relating to the age of the greenstones, I 
have always accepted the fact that the larger portion of the 
ereenstones of the lower levels were younger than the Upper 
Mesozoic coal measures, although I was, and am still, doubt- 
ful of the age of the massive greenstones of the more elevated 
regions, and such was, and is, my tentativeness of opinion, 
that, in my paper on the Geology of Bruni, read before this 
Society on April 13th, 1886, I stated—‘'That the opinions 
advanced by me have merely the force of probability, in my 
mind, from which all doubt has not yet been wholly removed ;” 
and again (p. 8), “I am only anxious for the truth of my 
Opinions, and therefore shall always be prepared to modify 
them in accordance with the weight of available evidence.” 
As yet I have not heard of any satisfactory reasons which 
would account for the position and relationship of the Bruni 
and Blackman’s Bay greenstones in such a manner as would 
favour an origin more modern than the Upper Paleozoic rocks, 
which appear to have been quietly deposited upon their upper 
irregular surfaces. I have considered the possibility of 
lateral thrust between the bedding on a gigantic scale, but 
there are still many positive objections lying beyond, which 
at present prevent me from accepting this solution. 
Tur REGIONS IN THE NEIGHBOURHOOD WHERE THE ForR- 
MATIONS AROUND LAKE St. CLAIR MAY BE STUDIED 
Most ADVANTAGEOUSLY. 
By confining his observations to the immediate shores of 
the charming Lake St. Clair, and to the romantic valleys of 
the Cuvier and Narcissus, Mr. Officer lost no advantage, so 
far as the lover of the picturesque is concerned ; but, so far 
as the profitable study of the particular geological forma- 
tions is concerned, he could not have chosen his field of 
observation more unfortunately. It is quite possible that if 
Mr. Officer could have obtained a view of the complete series 
of the rocks from the actual bed of Lake St. Clair, which is 
buried as much as 552 feet beneath the surface of its water 
level in the immediate vicinity of Mount Olympus, he might 
obtain a fair knowledge of the character and sequence 
of the typical rocks of this interesting locality. But although 
