BASALTS OF BATHURST AND NEIGHBOURING DISTRICTS. 297 
tion, but it is highly desirable that the knowledge thus gained 
should be supplemented by a chemical examination. I therefore 
determined, about two years ago, to commence a series of analyses 
of the various rocks of the district and also to have microscopic 
slides prepared from the same specimens, so that there might be 
no mistake as to the rock to which a particular analysis referred. 
A collection of rocks was sent to England to be cut by a very 
skilful workman, and I commenced my analyses of the pieces which 
T retained. Owing to the pressure of official work, however, I 
could only give a limited amount of time to analytical work, and 
as rock analysis is rather tedious, I found it would be a long while 
before I should be able to obtain anything like a complete series 
of analyses. I therefore decided to drop the granites and similar 
rocks for the time, and to confine myself to the basalts. 
The results obtained so far appear to be of considerable interest 
and worth placing on record. Basalts have been examined from 
various parts of the Bald Hills, from Mount Apsley and Mount 
Pleasant, two outliers in the neighbourhood, and from Rock 
Forest, a locality on the Macquarie River, about twelve miles 
below Bathurst. For comparison with these, sections of basalt 
from Oberon, thirty miles south-east ; Orange, thirty-six miles 
west ; Blayney, twenty miles south-west ; and Kiama, have been 
obtained and at any rate partial analyses made. For the most 
part, I have confined my attention to -determining the silica, 
alumina, oxide of iron, lime, and magnesia, these being the con- 
stituents of most interest in a basalt. 
Tn order to give a clear idea of what has been done, it will 
perhaps be well to describe briefly the various rocks examined, 
and then consider some of the questions which arise in connection 
with them. In order to render one’s remarks intelligible it will 
be necessary to give some particulars which have already appeared 
in print in the various papers to which allusion has been made, 
Mope or Occurrence or Batuurst Rocks. 
To commence with the rocks in the immediate neighbourhood 
of Bathurst. It will ‘be seen from the sketch map that the main 
