198 WALTER HOWCHIN 
found in the geological axes of the Mount Lofty ranges, Yorke 
Peninsula, and Kangaroo Island; the crystalline ranges of Eyre 
Peninsula, the porphyrite outcrops of the Gawler ranges, and the 
igneous and metamorphic plateau of Western Australia. 
In no instance has a glaciated floor been observed, the occurrence 
of which would suggest the probability of ice action above sea 
level. The absence of such an ice-marked floor, over the area in 
question, is not, however, to be wondered at when in no case have 
the glacial deposits been discovered in contact with a pre-Cambrian 
surface. The Cambrian till is found resting conformably on lami- 
nated quartzites in an orderly succession, and while the junction 
between the respective beds is always sharp and decided, it seems 
moderately certain that the glacial débris was laid down on a 
floor of contemporary marine deposits—in which case the agent 
of distribution must have been floating ice. This view is supported 
by the fact that the glacial material forms, practically, one con- 
tinuous sheet, spread over an immense extent of country, and 
maintains a remarkable uniformity as to thickness, lithological 
characteristics, and types of erratics throughout its entire extent. 
At the same time it is very probable that the ice-field was at no 
great distance from this area of deposit. Two glaciated erratics, 
composed of a very characteristic graphic granite occurring in the 
pre-Cambrian series of Yorke Peninsula, were found by the writer 
in the till on the Petersburg ranges, their probable source being 
150 miles to the southwest of where they were discovered. Among 
the erratics contained in the till, one of the most abundant is a 
porphyrite, which appears identical with the rock which comprises 
practically the whole of the Gawler ranges situated due west of 
the glacial deposit (I). 
PERMO-CARBONIFEROUS GLACIATION 
In its variety of features, wide distribution, and stratigraphical 
development, this must be regarded as by far the most important 
of the three periods of glaciation in Australasia. Glacial deposits 
of this age are represented in each of the Australian states, in- 
cluding Tasmania. In South Australia and Victoria the evidences 
are conclusive for the existence of land-ice during the Permo- 
