172 T. G. BONNEY AND F. T. 8. HOUGHTON ON MICA-TRAPS 
iWia ber sake: Pine BF, eo, 2:21 
CO ihe toh ieee 1°83 
IOLA Oy Ah TO 61:12 
ALOPH ROR. Cee aes 15:99 
Fel @: Avett eee 0-84 
MeO hx 0 had emer 1:70 
IN Gi Oar As eet eats: tr 
CAO Leia Site earn. eile} 
MICOS ee secre 2h: 4-93 
HCO Reise icc eno 4-80 
Nar OF ene eae 2:04 
100°58 
The potash probably belongs in part to the biotite, so, having re- 
gard to the large amount of lime present, it is clear the rock must 
be near to the plagioclase or kersantite group; but still it is better 
to name it minette-felsite. 
It weathers rusty brown, and occurs in Bannisdale Slates, being 
2 or 3 feet wide, much decomposed, breaking into large tabular 
masses along joints parallel to the sides, to which also the mica- 
flakes are often parallel. The adjacent rock seems hardly altered. 
(6) Dyke on Railway, W. of Docker Garth. 
Characters—Macroscopic. A compact grey rock, full of minute 
scales of brownish mica, with a rather silvery lustre, and indications 
of small felspar crystals. Specimen traversed by a vein of pink 
calcite. 
Microscopic. The ground-mass appears to be micro-crystalline ; 
but in parts there is indication of the presence of true crystalline 
structure, the outlines of felspar crystals being dimly discernible. 
These are often traced out by lines and clots of opacite. The ground- 
mass is much stained by ferrite, and traversed by acicular microliths, 
so that the original structure has been greatly obliterated. Mica is 
abundant, also dusty green patches of some decomposition-product, 
grains of iron peroxide (some magnetite), and some augite. 
An analysis gives :— 
Wiater aa ay eine 3°83 
COW Pi tree Moutencre ie (He, 
SILOM er anugerse a helen. 48°57 
ANE Gas Wesel ray atey pene 18:52 
Hei Org tee get ais utes: 1:60 
HeEO 37... aaa ae 6°87 
IME Oj ate ts ie ete ae 0:60 
CaO Fae ae eae 2°79 
MoO Pescin ie ere 8:97 
KI OR ee eae 8 O71 
INK OMR sc. See ene 1:59 
