ie THE HAWKESBURY SANDSTONE. 
“were cemented together by carbonate of — 
lime held in solution by rain-water. It was derived from the — 
recent shells which occurred not only in the sand but in the — 
clay. The cementing medium was also partly com 3 
peroxide. The result is a hard sandstone, not unlike one of much 
older date. 
It is a remarkable fact that stone derived from the wind-blowa — 
sand hardens by exposure, probably from the greater facility thus 
afforded for the formation of the great cementing medi 
of iron. The initial cause of the consolidation would of course be 
the pressure, and this is why we find in these formations the cores 
or centres of the highest and heaviest sand-hills. Still it must 
remembered that the strata of all these mountains are of a com 
pound nature, portions of them containing shales, which prov 
them to have been at one part of their history lagoons or marshes 
The fine aerial siliceous dust of which much of this rock is com 
and pressure of sand above. The hydrostatic pressure, — 
used to consolidate graphite, would be nothing to the effect 
thousands of tons of sand. 
Fine red sands.—Some of the Hawkesbury sandstone is of 8 
very fine texture, and of a peculiar salmon colour, which is plainly 
seen in some h broken masses. I was struck by the resem 
blance of its colour and grain to a thick deposit of sand Ww of 
fell on the Mosquito Plains on October 8, 1865. agp 
that year was particularly dry, and the hot winds set ™ 
id appearance, very much like dull copper in colour. fet 
no clouds, but a ; 
across 
Showed a rapid movement southward, The thunder 
and with a harsh metallic sound very different from the 
< Seamget 
from the south, and the sand was moving in a contrary®) seg 
iz ae ay f the atmospher The sand came from the 20 = 
