464 J. H. COLLINS ON THE SERPENTINE AND 
fault” referred to by Prof. Bonney as bringing up the rocks of the 
‘«« Archean Series”’ against the much newer slates, but which, as L 
think more probable, brings up the highly altered Lower Silurians 
against the equivalents of the ‘‘ Ladock beds,” which are, as stated, 
probably Lower Devonian. 
“* Talcose” Slates (Micaceous group of the Archzean series of Prof. 
Bonney).—In the immediate neighbourhood of the shattered rocks 
in the cove just referred to, may be seen a mass of greenish or 
brownish shales, very soft and apparently talcose, dipping steeply 
to the 8.E. I say “apparently ” talcose, because the greasy-feeling 
mineral is certainly not talc, the analyses showing that there is very 
little magnesia present. A little further on, as the serpentine is 
neared, these greenish and brownish shales pass into very soft red 
shales and mudstones, the change being evidently due to the peroxi- 
dation of the iron present. The following are analyses of the Porth- 
alla rock, and of the Lizard rock which is supposed to be its 
equivalent. I have selected both specimens as being as far as 
possible typical in their respective localities :— 
Porthalla. Lizard. 
Water lost in desiccator ... 0°15 | 0°10 
at SOO IO eee ce 0-00 2°80 0°85 
ps onignition ...... 2°65 - 0°75 
TLE ECE Vetee AA a eR CIs ne Aiebe 5 58°10 81-70 
PAU Tie) 1 celts Fae Ebest eeea ee eee eh 21°3 10°40 
IREETOUS, OXIDE «ey teseoe an, 3-04 
IRGrric OXIGE : i242. hee eae Bi eae QAO, -. 2S 
Mangcanous Oxid@ (1.52.20. 05.520 ceensesecseeas) | seecndeene een trace. 
Diavre STAs, A tae Oh LY. 0°72 0-40 
Masnesta: sf hiGhest a8 seen fetes 1-15 0-70 
Potash (with traces of soda) ......... 4°60 eee | “a ee 
99-10 99-96 
Sp: Pravily, c.cshi vst edeee-sscewens 277 2°612 
It is obvious that these rocks are essentially different, whether 
they be of the same geological age or not. 
The Gneiss or Granulite—In the upper part of the cliffs imme- 
diately to the east of the first fault, and extending as far as the 
broken ground which follows the second fault and somewhat obscures 
the first appearance of the serpentine, is a band or vein of granulitic 
rock (see specimen N). It consists essentially of nearly white 
quartz, pale pinkish soda-felspar, and a very little brown mica. 
Prof. Bonney regards this rock as a conformable bed of his micaceous 
series ; but I must say it appeared to me much more like an intrusive 
vein, not coincident either in bedding or strike with either of the 
other rocks. It is not very easy to get up to this rock in the cliff 
face, but specimens are easily obtainable from the great blocks 
which strew the shore. I believe it is the same rock which occurs 
in large partially rounded masses in the conglomerate between 
Porthalla and Nelly’s Cove ; at any rate they are identical in appear- 
ance, both macroscopically and microscopically. They agree also in 
chemical composition, as will appear from the following analyses :— 
