416 Miss C. A. Raisin—Rocks from Somali Land. 
Tn the quartz, along continuous surfaces, are rather large fluid 
cavities with moving bubbles. The granite seems somewhat dis- 
integrated ; the quartz grains, and, at places, the felspar, are coated 
with a bright red deposit. Some of this ferruginous substance 
appears under the microscope minutely pisolitic, and the small 
concretions are sometimes banded concentrically like spherulites. 
Metamorphic Rocks. (1.) Gneisses.— One specimen is a white 
micaceous gneiss, with small garnets. From the appearance of the 
rock, Professor Bonney has suggested that it may possibly have been 
once igneous, although there is now an evident foliation, and the 
eneiss has suffered contortion since the foliation was acquired. 
In a pale red or flesh-coloured gneiss, the quartz is ranged in 
streaks very suggestive of the action of pressure. The felspar is 
mainly plagioclase, with possibly some microcline, and either exhibits 
a kaolinized condition, or seems to pass to a clear mineral with lines 
like the distinctly marked cleavages of kyanite, suggesting the possi- 
bility of the formation of clear pseudomorphs similar to those noticed 
by Prof. Bonney.' | White mica seems to have developed in places at 
the expense of the felspar. 
A banded hornblendic gneiss contains hornblende, which is very 
dichroic and possibly of two varieties. It is replaced in the paler 
bands of the rock by brown mica, associated with quartz, and also 
with felspar, which may be partly kaolinized along certain of the 
twinned lamine. Small irregularly formed garnets occur, salmon- 
pink in colour, within a cloud of kaolinized substance and associated 
with flakes of biotite, as if they had formed from original felspathic 
material by the addition of iron and magnesia, while the brown mica 
was developed in connection. 
(2.) Tale Schist.—This specimen seems to have been artificially 
cut, as if the rock may be used as a kind of potstone. Under the 
microscope, the slide exhibits an interfelted mass of talc, together 
with a pale apple-green mineral, which is sometimes very dichroic, 
and would agree with prochlorite in its softness. Some magnetite 
occurs, and a reddish iron glance in such quantity that the section 
has a brownish colour. The chlorite has much the appearance of a 
pseudomorphous formation after some mineral, very probably biotite, 
and it helps to give the orientation of the slide. The foliation 
appears to have undergone subsequent disturbance, amounting to a 
crumpling and even an approach towards an “ ausweichungsclivage.” * 
(3.) Epidote Schist or Epidosite.—Said to occur near the foot of 
the hills, and it would probably belong to some part of the earlier 
series of rocks, which form the foundation of the higher ground. 
The specimen consists mainly of epidote, the quartz being probably 
not more than 10 per cent. of the whole rock. The epidote is 
mostly granular, but some of it is in larger crystals, which exhibit 
cleavage. The quartz grains are drawn out in the direction of the 
general orientation and sometimes ranged, almost in single file, in 
thin parallel bands. A few small crystals of hornblende occur. 
1 Q.J.G.S. 1878, Pre-Carb. Rocks of Charnwood, part i. p. 215, note. 
2 « An advanced stage of minute puckering, some or all of the surfaces of contrary 
flexure having become shear-planes.” (Teadl’s Petrography, p. 424.) 
