AUSTRALIAN GLACIATIONS 197 
scratches, cross each other in various directions, and are cut into 
the stone to varying depths. Most of the elongated erratics are 
fractured transversely, with numerous gaping fissures which are 
sometimes filled with fibrous quartz (illustrated in Fig. 1). These 
fractures have probably resulted from strain acting along the 
planes of cleavage which has pulled the stone apart in successive 
planes. 
It is a somewhat difficult task to restore, in imagination, the 
physiographical conditions that prevailed at the remote period 
Fic. 3.—Glaciated erratic (quartzite) from Cambrian till, Umberatana, Flinders 
Range, S. Aus. 3 natural size. W. Howchin, photo. 
when this morainic material was laid down. From the nature of 
the evidence it is believed that the chief agent involved in laying 
down so vast a sheet of glacial débris was floating ice in an open 
and extensive sea. This sea was probably bounded on the south 
and west by moderate highlands, consisting of pre-Cambrian 
(Algonkian) quartzites, schists, limestones, and other sediments 
with exposed igneous batholiths and dikes of varied types. The 
pre-Cambrian complex had been subjected to great waste and 
was probably in the form of subdued relief at the time of the Cam- 
brian glaciation. Remnants of this pre-Cambrian continent are 
