504 Miss C. A. Raisin—Rocks from Socotra. 
the outer waters of the ocean were dissevered from those of the 
Jordan-Arabah lake by the up-rise of the land, there is no evidence 
that there was ever any subsequent connection by means of a stream 
flowing down from the North into the Gulf of Akabah. The closest 
approximation which, according to my view, these inner and outer 
waters ever made towards each other is represented in the sketch- 
map of that whole region in page 72 of the Geological Memoir, 
where a tract of ground of about 40 miles in length and rising to 
700 feet in height is represented as intervening between their 
respective borders. 
VIII.—On Some Rocx-Spectmens From Socorra. 
By Miss C. A. Ratsin, B.Sc. 
I Vara specimens were collected in Socotra, near the coast, by 
Colonel M. Gosset, and were sent to Prof. Rupert Jones. By 
the kindness of Prof. Bonney I have been allowed to carry on the 
examination of the rocks, at University College, in connection with 
the Somali specimens already described. 
Granites.—The granites need little description, as they are clearly 
of types already obtained from Socotra;! they consist chiefly of 
felspar, often microcline, and of quartz. Hornblende crystals, 
evidently of early consolidation, are imbedded in the felspar. Some 
of the hornblende is very strongly dichroic, and changes from a faint 
green to a deep peacock-blue, tints which approach somewhat near 
those shown by glaucophane. Octahedra of magnetite occur in one 
fragment, and in others characteristic crystals of zircon are fairly 
abundant. 
Felstones.—Many of these seem to be quartz-felsites of the red 
and purple tints, mentioned by Prof. Bonney as so characteristic of 
Socotra. Two specimens, however, need somewhat fuller description. 
(1). Quartz-felsite. This is a very compact, flinty rock, dull-green 
in colour, blotched with white. The ground-mass is completely 
devitrified, with small brightly-polarizing microliths scattered 
through it. The porphyritic hornblende is in partial preservation, 
but frequently epidote appears to have formed along its cleavage- 
planes, and spread over the interior of the crystal. Many of the 
felspars are plagioclase; some have passed to an aggregate of 
crystalline films, but others appear clarified, with kyanite-like 
cleavages. The porphyritic quartz is much corroded. Some of 
the embayments formed of the ground-mass inclose clear, unaltered 
quartz, generally with a shadowy outer border, as if it had been 
partially melted down by the surrounding matrix (Fig. 1). In 
other examples, the invading ground-mass, which has an angular 
outline, stops short of a curved boundary, marked out by minute 
cavities often with moving bubbles. Corrosion of crystals has been 
attributed to the influence of a direct rise of temperature, or 
indirectly to some cause which increases the fusibility of the matrix 
and solubility of the crystal, such as an alteration in the amount of 
' Phil. Trans. 1883, p. 282, On a Collection of Rock Specimens from the 
Island of Socotra, Prof. Bonney. 
