i 
294 ON ROCK SPECIMENS FROM THE ISLAND OF SOCOTRA. 
3. Junction of felsite and granite. Haggier range, near Adona (p. 285) X 20. 
(a.) Very compact felsite. 
(b.) Crushed granite. 
(c.) Granite. 
Drawn with polarized light. 
4. Rhyolite with spherulites. Azorah district (p. 287) X 40. 
Selected as a fairly typical example of a rather frequent type of rock. 
5. Rhyolite exhibiting “ flow brecciation,” near Azorah (p. 287) X 20. 
The dark streaky part (a) is the general ground mass of the rock in which 
fragments are entangled ; (b) exhibits small latli-like crystals of a decomposed 
felspar in a ferrite stained ground mass somewhat resembling that of the last 
slide ; ( c ) exhibits a minute “ speckled ” devitrification structure ; (cl) with a 
high power exhibits minute felspar microlites crowding a dark ferrite-stained 
base, while in the centre of the slide is a fragment showing a well-marked fluidal 
structure, the lighter parts of which are devitrified. It is of course possible that 
some of the fragments may be entangled lapilli, but the absence of a slaggy 
border and the general cleanness of their edges corresponds better with the idea 
of their having formed parts of the flow. 
6. “ Trachyte ’ with minute amygdaloidal cavity. Near Azorah (p. 287) X 30. 
The minute felspar microliths are slightly more evident in the slide than in 
the drawing, and one or two of the cavities are larger than that figured, but 
unfortunately them contents have partly torn away in grinding. 
