BY R. M. JOHNSTON, F.L.S. 105 
throughout the mountains and lowlands of the island. At 
the time of eruption, probably recurring at intervals 
over a long period, it seems as if the conditions for 
plant life were everywhere impossible. There is no 
evidence at this time of glacial phenomena,* but as Mr. 
J.S. Gardner has arrived at the conclusion, from the study 
of fossil floras and “strong negative and positive evidence,” 
that, although there were no intense glacial effects, there were 
alternating warm and colder conditions produced, most pro- 
basly due to astronomical causes alone, and therefore it 
seems probable that our great eruptive period, which destroyed 
our Mesozoic flora, may have been concurrent with a cold 
epoch,* due perhaps to less intense eccentricity of the earth’s 
orbit, and thus showing a correspondence with the next great 
eruptive period (basalt) which, concurring with more potent 
astronomical and geographical conditions, during our glacier 
epoch at the commencement of our Neogene period (Pliocene), 
the whole of our rich and varied Tertiary flora was similarily 
suddenly and almost completely destroyed, locally at least. 
These three great changes in our flora, therefore, corres- 
ponding with the exceptional glacial epochs, and also corres- 
ponding closely with the periods of great physical convulsions, 
go to show that there is an underlying bond of connection 
with exceptional concurrences, at remote intervals, of astro- 
nomical, physical, and geographical causes,t and that the 
combination of the three latter causes is essential to the initia- 
tion of conditions which produce glacial epochs contem- 
poraneously in widely separated parts of the globe. The 
universality of ylacial action towards the close of the Permo- 
Carboniferous age is testified by the following observations of 
their occurrence in rocks of different countries. 
EVIDENCE OF GLACIAL ACTION IN Rocks OF THE 
PERMo-CARBONIFEROUS AGE. 
Lasmania.—lt is fully nine years ago (1884) since I first 
communicated to the Royal Society of Tasmania my discovery 
of evidences of ice action in the rocks of Permo-Carboniferous 
age at Maria Island. In the year 1886 I made a farther dis- 
covery of similar evidences of ice action in the shape of huge 
erratics and polished blocks of the harder rocks foreign to 
the neighbourhood, in the same formation, at One Tree Point, 
* Dana recognised the close of the cretaceous period as “an epoch of cold.” 
+ This conclusion is in harmony with the originally expressed opinions of 
Agassiz and Dana, according to Dr. Wallace’s account (p. 222—‘‘ Island Life).” 
“‘ Agassiz appears to have been the first to suggest that the principal epochs of life 
extermination were epochs of cold ; and Dana thinks that two at least of such 
epochs may be recognised at the close of the paleozoic and of the cretaceous 
periods.” To which we may certainly in Australasia add a thirdat the close of the 
paleogene period (miocene) concurring with the great glacier epoch of Australasia. 
H 
