BY R. M. JOHNSTON, F.LS. 125 
The difficulty of explaining these facts by reference to a 
cause which only came into operation at a much later period; 
z.é., in the Pleistocene glacial epoch, and which forms the 
greatest stumbling block to the acceptance of the potency of 
the astronomical theory as being alone sufficient to account for 
such a refrigeration of climate as that which produced the 
intense glacial epoch of Hurope, is next discussed by me in 
the same place at considerable length—pp. 255, 256—and the 
following conclusions were arrived at:—“ Accordingly from 
the very much smaller proportion of elevated land in the 
Southern Hemisphere, and from the improbability of the 
equatorial ocean currents having been appreciably excluded 
at any time, owing to the absence of connected land barriers, 
it is reasonable to infer that the combined effects of 
astronomical and geological causes, similar to those which 
brought about the glacial epoch in Europe and North 
America (but especially to the favourable latitudinal position)— 
are not likely to have operated intensely in Australasia. 
“That this seems to be the more reasonable view as regards 
Australia is borne out by local evidences. 
“In the first place the Neogene epoch of Australasia 
corresponds with the Pliocene epoch of Europe, and, con- 
sequently, whatever the local climatic conditions may have 
been, they cannot in all respects be referred to causes which 
entered into combination in a succeeding epoch in the 
Northern Hemisphere. 
“In the second place, while admitting the evidence of former 
glaciation in local alpine regions, there is no satisfactory 
proof that the erratics found in such regions belong to the 
period in which our raised terrace drifts were formed; and 
neither in these nor in the later deposits of the extensive 
lower levels do we find any clear signs of ice action, such as 
are exhibited so widely in Europe and America, in the shape 
of moraines, boulder drift, striated blocks, perched blocks, 
and other huge ice-borne erratics, etc. On the contrary, the 
prevailing terrace drifts in Tasmania are formed from 
materials derived from the adjacent or underlying rocks; 
and with the exception of huge boulders at the base, or on 
the slopes of mountain ranges, clearly traceable to gravita- 
tion, there is not the slightest trace of rock masses which 
would necessitate the agency of ice as a means of transport,* 
if we except also thoseevidences (z.¢., of glacial action) in alpine 
regions in the western highlands, which are more probably 
local effects due mainly to a much greater elevation of the 
land in former times (and I am now able to add, perhaps, 
also the influence of the greater limit of the eccentricity of 
* These remarks do not apply to the ice-borne erratics found in rocks of Permo- 
Carboniferous age, of which there is the most abundant evidence throughout the 
older mudstones of this age in Tasmania, Victoria, and New South Wales. 
