BASALTS OF BATHURST AND NEIGHBOURING DISTRICTS. 507 
it is unlikely that various specimens selected for analysis would 
all contain the same proportion of constituent minerals, A 
specimen rich in olivine would be likely to show a high percentage 
of magnesia and iron ; one with an excess of augite would probably 
be rich in lime, while a large amount of felspar would bring up 
the alumina percentage. 
SPEcIFIC GRAVITY. 
The Bald Hills rock gave results ranging from 2°9 to 3-05. 
That from Apsley was nearly the same, about 2°9. The Mount 
Pleasant rock is lighter, three specimens all giving about 2°68. 
COMPARISON WITH OTHER CENTRES. 
One naturally desires to find out the source of our Bathurst 
basalts. Around Bathurst itself there are no indications whatever 
of old craters or voleanic necks from which the basalt might have 
been erupted, but within a radius of forty miles there are three 
districts where basalts and allied rocks occur under conditions 
which render it likely’ that they were once centres of volcanic 
activity. These are, 1. The Blayney-Carcoar area, 2, The Orange 
district and, 3. That of Swatchfield. Map 2 shews the relative 
position of these centres, and it will be seen that all are at 
considerable, and not very unequal distances from Bathurst. If 
we take Carcoar. as a possible centre, that is about thirty miles 
away. The Canoblas, near Orange, are about thirty-six miles, 
and the Swatchfield area is about thirty-five miles distant. 
Blayney—This town is rather over twenty miles from Bathurst 
ina south-easterly direction. It is the centre of a very interest- 
ing district, where a great variety of rocks occur, and would well — 
repay detailed geological study, which would, however, entail long 
and careful work on the spot. One finds, within a short distanco © 
of the town, granites sending veins into the altered contact rocks, 
such as are so common around Bathurst ; schists, phyllites, of — 
various types, with beds of limestone carrying fossil corals. 
There are also veins of copper ore which have been worked to_ 
a considerable extent and, what is of more immediate importance, : 
intrusive dykes of basic igneous rocks, together with basaltic one 
