579 
“Near Inverell the Pliocene basalt contains large crystals of hersclielite, with 
analcime and aragonite, also small rounded masses of olivine. Basalt of the same age 
caps the Bald Hills, near Bathurst; it here exhibits columnar structure.” 
Beferring to the basalts and associated drifts of New England, Mr. T. W* 
Edgeworth David says * : — 
“ During the greater part of that vast period of time (the Mesozoic) the surface 
of the land was being slowly brohen up and worn down by the action of rain, frost, 
sunshine, vegetation, and perhaps marine erosion, until a land surface was evolved, 
which in its broad features resembled the present. Vast thicknesses of sedimentary 
material having been removed by these means, the underlying crystalline rocks were 
laid bare, and, erosion proceeding still further, the crystalline rocks themselves and 
their metalliferous veins became disintegrated and their materials transported and 
redistributed by water. In this way were formed the deposits of gravel, of which the 
outliers at Scrubby Gully and Ruby Hill are the insignificant remnants. The intensely 
worn surfaces of the pebbles in this gravel, and the fact that only the hardest and most 
indestructible minerals — as quartz, tinstone, and gemstones, &c. — have survived in them, 
shows that they must have been subjected to a long process of battering and bruising, 
in which the weaker pebbles of claystone, granite, &e., were completely pulveri.sed. 
The only power iir nature capable of doing such a work is the sea, where it breaks on a 
roclcy coast. These Tertiary gravels are, therefore, probably of marine origin, a fact of 
great significance as bearing upon the probable richness of stream tin of the ‘ deep 
leads,’ for marine beds must have had a wide extent, and the great richness of these 
small outliers favours the expectation that the far larger portions which have been 
swept away wore equally rich ; so that large bodies of ore derived from this source must 
have gravitated into the lower level gravels subsequently buried under lava. As the 
land continued to rise the sea would recede further west, and the rivers being increased 
in size and power subaerial degradation would proceed more rapidly. The channels of 
the rivers would be continually deepened, and the whole surface of the land gradually 
lowered to adapt itself to the increasing fall of the rivers. The three terraces of gravel 
at the Surprise Minos mark the levels at which the bottom of a large river stood at three 
successive epochs. What was the exact configuration of the country at the time of the 
first outburst of the basalt lavas geological evidence fails to tell. That part only which 
has been scaled up under the lava sheets has been preserved to the present day, and its 
shape is being gradually restored by the workings on the ‘ deepi leads.’ The results of 
these subterranean explorations tend to show that most of the country now covered by 
lava sheets, and forming in places main linos of water parting, was at that time near to 
or part of the principal drainage channels, and that the trend and fall of these 
old rivers agreed approximately with that of their nearest modern equivalents. Of 
course there are no exact modenr representatives of these old streams, nor is it always 
possible to determine, even approximately, with what present rivers they should be 
correlated. At the Pishing Grounds, however,. near Kangaroo Plat, there can be no 
doubt that the old stream, which produced the coarse shingle now capped by lava, was 
related to the present Beardy River. The bottom of the channel of the Beardy at the 
nearest point, one mile di.stant, is now 550 feet below the level of the bed of this buried 
river channel. The flora of the period, to judge from the number and variety of leaves 
entombed in the Eocene pupeclays, was rich and diversified. The fossils are chiefly 
leaves of herbs, trees, and ferns, some having fruit, and one a blossom delicately 
* Geology of the Vegetable Creek Tin-Mining Field, by T. W. Edgeworth David. Mem. Geo!. 
Survey N. S. IVales, 1887, p. 58. 
