248 JOURNAL OF THE PLYMOUTH INSTITUTION. 
E. Scoriaceous-Lava, Egg Buckland.—Hard, slaggy rock, some- 
what approximating in substance to a pitchstone. Under the 
microscope the matrix is seen to contain lath-felspars. The 
crystals shown in sketch are porphyritic orthoclase-felspars. ‘There 
is a little iron oxide in these crystals, but more in the matrix, - 
especially round their edges. ‘There are also vesicles, some of 
which contain calcite, others plagioclase. In another example of 
the same series there are vesicles with a lining of plagioclase and 
a central filling of calcite. 
F. Tuff, Saltash Bridge, Devon end.—Ochreous-drab, soft, 
schistose-granular, with spotty look and scaly texture. This is a 
very interesting rock, which might perhaps be called a lava-breccia. 
It consists of broken felspars, fragments of volcanic rock, and 
other clastic material, In an apparently fluidal matrix, partially 
vesicular. 
G. Tuff, Compton.—This rock has a curious granular-schistose 
character; the schistose intervals appearing like impersistent 
slaty lamine. The grains are chiefly felspar and quartz, with a 
- little calcite. The interstitial matter was probably volcanic dust, 
which has consolidated under pressure, though some of the 
patches have what appear to be minute vesicles, while others 
show microliths. Some ferrite is present. 
H. Lapilli in slate, Drake’s Island.—A greenish slate contain- 
ing fragments of volcanic rock, one of the most characteristic of 
- which, with lath-felspars and crystals of magnetite or pyrites, is 
shown. 
I. Picrite, Clicker Tor.—This is the rock commonly known as 
Menheniot serpentine. Originally an olivine-dolerite. The olivine 
has chiefly been converted into pale green serpentine, and the 
main feature of the section is a crystal which has undergone this 
change. Augite, and magnetite, and pseudomorphs after felspar 
are also present. 
K. Dolerite, Ernesettle.—A grey crystalline rock, with flesh- 
coloured crystals of felspar, and dark crystals of pyroxene. The 
microscope shows augite, hornblende, viridite, plagioclase-felspar, 
magnetite, ilmenite, and apatite. There has evidently been much 
alteration. Weard, Notter, and Treluggan are of the same class, 
