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PROCEEDINGS OF SECTION C. 
angle of 1 degree, or 1 in 57, would give a thickness of 460 feet for 
an outcrop of 5 miles wide; and from the evidence afforded by 
numerous bores I am prepared to admit that this thickness is by no 
means overestimated. 
Hitherto it has been convenient to speak of the series of beds 
designated the Blythesdale Braystone as being of similar composition 
throughout. This, however, is not the case, as the braystone of 
normal composition is “ parted ” in places by beds of sandy shale 
and calcareous sandstone. We may imagine coarse sandy and 
gravelly sediments brought down to the margin of a shallow Lower 
Cretaceous sea by numerous tributary rivers, and spread out along the 
shore and out to sea by the action of waves and currents. Such 
material could only travel along the bottom, being too coarse and of 
too high specific gravity to remain in suspension, as a general thing, 
far from the mouths of rivers. The influence of wave-action, at least, 
would cease when the sea attained even a moderate depth. I am 
inclined to believe that the sea in which the Blythesdale Braystone 
was deposited and distributed — viz., the sea which divided the Aus- 
tralian continent from north to south into two islands — was very 
shallow throughout, and may have been swept from end to end by 
currents sufficiently powerful materially to aid wave-action in the 
distribution of the sand and gravel. Otherwise I do not knowhow to 
account for the wide distribution of the sand and gravel which is 
evidenced by the artesian wells. I imagine, further, that the later 
but continuous period to which the argillaceous Lower Cretaceous 
deposits belong was one in which a marked subsidence of the interior 
of this sea took place. The wide distribution of the Blythesdale sands 
has a parallel in a newer geological period in the enormous extension 
of the Desert Sandstone. Unless I had seen it with iny own eyes, I 
should have had a difficulty in conceiving that heavy gritty sand could 
be so widely distributed as it is in the latter case; but, having seen it, 
I can believe that the Blythesdale sands may be equally extensive. 
It may be assumed that the Blythesdale and Desert Sandstone 
periods were both characterised by heavy rainfall, producing rapid 
denudation of the land, and possibly by prevalent rough weather at 
sea, causing violent wave-action. At the same time the intercalation 
of some argillaceous sediments among the Blythesdale braystones need 
cause no surprise, as they would be the natural result of occasional 
spells of dry weather on land or comparative calms at sea. The wonder 
is that there should be so few. It is not likely that the intercalated 
argillaceous sediments are continuous over the whole area occupied by 
the Lower Cretaceous formation. They are more likely to be lenticular 
at the margin, and to spread out and thicken towards the interior of 
the area. The Blythesdale Braystone, therefore, although it may locally 
be split up into two or more beds by the intercalation or comparatively 
impermeable strata, I believe to be practically a continuous deposit. 
It lias already been mentioned that the Blythesdale Braystone is, 
over a large area, covered by the Desert Sandstone. Taking this into 
account, and also the fact that the actual breadth of the outcrop, where 
it is not covered by the Desert Sandstone, has not been mapped, we 
are still uncertain of the total area of the outcrop. I think, however, 
we are safe in assuming an average breadth of about 5 miles. In his 
Annual Report lor the year 1892, Mr. Henderson made what I then 
