ae yet fi > : Wer 
SN 
40 ON THE CHEMICAL ComPosITION OF CERTAIN ROCKS, Ki 
al i Slate, Cox River.—Bluish-grey colour, somewhat weat 
slightly fissile. Of Devonian age. 
ie Specific gravity, 2-706 at 21° C. 
ris Analysis. 
Hygroseopic moisture at 100° C ...... “861 
Combined »y  bydifference... 5°106 
Silica 61°012 
Alumina 21°34: 
Iron sesquioxide 3°704 
: ys, protoxide 2°109 
oe Manganese protoxide ‘729 
er Lime ..... ‘ 1‘176 
ee scan gta get eee REET ‘887 
otash 1223 
oda ., 1°850 
- 100-000 
 _ The combined water is estimated by difference, on account of the : 
difficulty of completely driving off and collecting the whole of the 
water in the hydrated silicates of alumina. ‘ 
: : Shale, Wallerawang, of a slate-grey colour, full of white impr — 
_- _ Stons of glossopteris roots, fronds, &e. ; fairly hard, and somewhat 
ty. Contains a little carbonaceous matter. : 
Specific gravity, 2-304 at 20°6 C 
4 Analysis. 
: Hygroscopic moisture at 100° ......... 1115 
Combined water and organic matter 6°391 
RHOW os. seciluasiss vg ee 
Alumina and traces of iron .......... 17°736 
ci ee Oe. | in fF | 
4 Potash .......;,; “466 
Ni le OGN Gor 383 
: 99°722 
“one Slate, Wollondilly River, from above Goulburn, of & “ . 
A ieee bluish-grey colour, imperfectly fissile. 
os Specific gravity, 2:58 at 18° O. 
ag Analysis. 
Hygroscopic moisture at 100° C. ...... ‘301 
Combined : with carbon- 
_.. aceous matter 3:990 
— ela eigas pie! 
umina and traces of iron ............ 16°4 
Manganese protoxide traces 
Magnesia .... oe 
BERETA "708 
: Potash ......, 2-274 
100°231 : 
A second specimen yielded silica, 77°54, and only 1076 % 
