518 NEW SOUTH WALES. 
amygdaloidal rock had flowed ; for such air-cells would necessarily be 
lengthened in that line. In the case in question, we have not only 
oblong cellules, and the evidence they afford, but we have these cel- 
lules large at one end, and drawn nearly to a point at the other, with 
the pointed ends all lying the same way: and as their direction is to 
the eastward or towards the sea, we conclude that the eruption 
occurred somewhere to the westward or northward and westward. 
Some of the dikes of the cliffs appear to have had a connexion with 
the outbreak, but most of them belong to a subsequent era, as they 
intersect also the sandstone above. 
A second eruption of basalt took place after the other accumulations 
of material had been made, which produced a layer of sandstone over 
the preceding bed. But this sandstone contains no fossils. 
The extent of the destruction experienced cannot be known; for 
in few places the fossiliferous layers below the coal outcrop above 
the level of the sea. ‘The Hunter region is an interesting place for 
their study ; but my own time did not allow of sufficient exploration. 
The same alternation of basalt and sandstone, and apparently of the 
same age, occurs in Van Diemen’s Land; and we may therefore infer 
with reason that Illawarra was by no means its limit. Yet 1t appears 
that the eruptions were to a great extent local, though they may have 
been numerous ; for in Illawarra only the southern half of the district 
was covered by them. For while the coal series lies upon the basalt 
to the south, there is to the north nothing intervening between it and 
the lower sandstones. 
The influence of the heat, through the diffusion of hot waters, 
caused, however, the disappearance of animal life, simultaneously, in 
both extremities of the district, and there is also evidence, that the 
northern portion was removed somewhat from the source of heat in 
the fact that the fossils are less perfectly silicified, or not at all so. 
We have thus made out the character, course, and effects of the 
Illawarra basaltic eruptions. Similar eruptions occurred in various 
parts of Australia to a much later period, the age of which remains 
to be determined. 
We next pass to the coal deposits. 
The first incident of the coal era which we notice, is, that the region 
before under water had become dry land, a fact of which we have de- 
cided proof. For there are traces of just such pools made by standing 
water, as would and do occur in low flats, along the shores of a sea. 
We have spoken of thin beds of clay-ironstone, often but two or three 
