296 SCOTT’S LAST EXPEDITION 
rocks of Western Australia, or Eastern Canada—that is, they 
are of pre-Cambrian age. They were laid down for the most 
part by the agency of water, the schists and limestones being clays 
and chalks when they were formed. The sea-bottom on which 
these deposits collected was subject to continual up-and-down 
movements, changing the character of the deposit, for we find 
in rapid succession and in thin layers schists which were fine muds, 
next to quartzites which were sandbeds, and marbles which were 
either deep-water chalk deposits or shallow clear-water coral 
reefs: 
On account of the complex folding of these beds, as well as 
the difficulty of obtaining a measurable section, we are unable 
to make any definite statement as to their thickness, but they can- 
not have been less than 15,000 to 20,000 feet. But figures are 
of little value, since there is no method of ascertaining what thick- 
ness of strata has since been denuded from the surface. The 
folding and heating of the rocks has since quite destroyed all 
evidence of the animal or vegetable life of that time, though 
numbers of small graphite particles, found in the crystalline lime- 
stones, may be the remnants of carbonaceous growth in the an- 
cient coral reef. 
Our earliest view, therefore, of the region is that of a sea 
bordered by land long since used up in forming these deposits 
of mud, sand, and limestone. The gneisses were in some cases 
huge intrusions of granite connected with the up-and-down move- 
ments referred to, and in other cases conglomerates, formed 
close to the coast-line by waves or rivers. It is probable that 
there was life of the lower forms in these seas, their skeletons 
being now altered beyond all recognition. 
Between the deposition of the crystalline schists and the 
next succeeding strata there is a vast gap, yet the mere existence 
of a gap in the geological record means something, and we may 
interpret it as marking a period of uplift in that area, so that it 
was dry land, and instead of receiving further deposits, became 
the source of deposits laid down in neighbouring seas. In the 
vast period of time that this gap represents, most of. the altera- 
tion and folding of these rocks took place, for the later strata 
are comparatively undisturbed. ‘The mechanics of these huge 
earth-movements are hidden from us, but they partook of the 
character of a shrinkage, and the strata were folded and plicated 
