BY R. M. JOHNSTON, F.LS. 75 
referred toas to forget the claims and importance of the 
others. It is well, therefore, from time to time, that we 
should have our attention aroused to the claims and interests 
of branches of geological study outside of that to which each 
of us, respectively, may happen to be too deeply immersed. 
We therefore cannot realise the benefits of such papers as 
that of Messrs. T. B. Moore and A. Montgomery, M.A, 
which arouse us from our own favourite grooves and recall 
our attention, for a time at least, to that large and important 
phase of Dynamical Geology known as Glacial Action. This 
phase also at once inevitably leads on to considerations as to 
its cause or Cosmical aspect ; to its effects as in its Stratigraphical 
and Phystographical aspects; and to the period of its manifesta- 
tion as in its Chronological aspect. 
Before we enter upou the question of evidence as to the 
occurrence of a former climate in Australasia sufficiently 
intense to be designated “A Glacial Epoch,” we must briefly 
consider the character of the evidence by which we infer its 
actual occurrence. It is obvious that we cannot directly 
approach the subject of the earth’s temperature at a former 
period ; for the original cooled air and the frozen water cannot 
be conceived to be stored up and preserved for observation, 
as in the case of ancient forms of life preserved in the rocks. 
But while drectly we can gain no information as to tempera- 
ture, we have abundant evidence preserved of the effects, 
which, according to our present knowledge, can only have 
been produced by an intensely low temperature acting upon 
watery vapours while subjected to the universal law of gravita- 
tion. It is, therefore, clear that itis in the preserved dynamic 
effects of moving masses of snow or ice, and, negatively, in 
the poverty or total absence of life forms that we have the 
best, if not the only, means of inferring the severity of the 
climate of a former period. 
Evidence of ice action derived mainly from the Study of 
Glaciation in the Northern Hemisphere. 
We have at present in the Alpine regions of Europe, Asia, 
America, and New Zealand, ample means for determining for 
various Jatitudes and for varying levels the peculiar or 
characteristic effects produced by a long-continued low 
temperature upon water vapours and upon forms of organic 
life long exposed to it, and we have also obtained, by 
the careful researches of many skilled observers, very clear 
knowledge of the dynamic action upon rocks of the frozen 
Snow and ice in gravitating from the higher to lower levels ; 
of its transporting and abrading power over higher and lower 
land surfaces, as in boulder-till deposits in roches-moutonneés, 
and scooped lakes ; and of its peculiar modes of discharging its 
