THE HAWKESBURY SANDSTONE, 5° 
quartz), even though the surface has been 
the rie of blown sand. i 
"S ] 
eee 
; nese contin exposed | 
_ the action of blown sand from the desert, and the members can 
judge of the effect of this from actual inspection. It can be seen 
the constant impact of blown sand has given the stone a 
~ most brilliant polish, but at the same time not a single angle has 
‘worn away. If the pebbles found in the Hawkesbury rocks 
“donot ot bear a more evident polish, the cause must be looked for 
in their long entombment, But the facts remain that the surfaces 
of the pebbles are generally abraded, not rounded as they would 
be were the action that of running Menara The exceptions may 
Well be due to creeks, as they are so uncom 
With regard to Professor Liversidge’s suateney I have first to 
him for the information he has afforded us on those matters 
about which I especially appealed to him. I have not expressed 
_ lnyself decidedly about the hyalite, though I threw it pt as a 
‘iggestion that polarized light gives a good test for its detection. 
But we must not expect very Spreab results from this method, 
_ because if the original grains were derived from granite, some of — 
the quartz from that rock _presents under the Nichol prisms the 
Play of colours observed in colloid silica. the beginning of 
_ Y microscopic work in this matter, I was inclined to think the 
Polarized light and the selenite plate would give me definite 
i thy § y 
_hyalite, the results were conflicting. Iam going to try again at 
Biting sections of the rock, and then I am in fies that the 
ae in the cementing medium may be better seen. My friend, 
ir. Wilkinson, does not believe that the > grains of sand will 
any clue ; t 
matter, 
‘that j in the matter of conglomerates I went out of my 
exp which 
la my theory. Still, I differ from Professor Lin e 
this, sree do in forming pebbles in such a formation : 
oxides of j iron, ——— Sipe of ie aoa, | 
lain a feature which, whether explained pan ec, By ; 
