250 JOURNAL OF THE PLYMOUTH INSTITUTION. 
S. Chiastolite-Slate, Ivybridge.—The sections of chiastolite are 
seen clearly to show the “cross markings” whence they take their 
name. The light patches are probably imperfect’ crystals. 
T. Junction-Rock, Cornwood.——This section shows the actual 
junction between a fine-grained, light pinkish-grey granite, and a 
micaceous-schist. The mineral developed in the centre, along the 
line of junction, is mica. On one side we have granular felspar, 
quartz, and mica; on the other (the lighter) felspar and quartz, 
with apparently minute garnets. | 
U. Schorlite, Shaugh. — Fine-grained, dark-grey mixture of 
schorl and quartz, with cavities containing needles of achroite and 
epidote. The microscope shows the schorl to be chiefly prismatic- 
granular, blue and yellow, and the quartz, the light portion of the 
slide, to contain enclosures. 
V. Elvan, Colwell.—A couple of porphyritic blebs, rather than 
crystals, of quartz are shown in the midst of the granular felsitic 
matter, with a little ferrite or manganese. 
W. Basalt (1), Cawsand.—Red, dull, semi-vitreous rock, with 
porphyritic felspars, partly changed into felsitic matter. Crystals 
of mica, as in lower right of slide, well developed. General base 
felspathic, coloured by iron oxide. 
X. Gneiss, Eddystone.—This rock contains quartz, orthoclase 
and plagioclase felspars, two micas, garnet, titanite, and, according 
to Mr. Tawney, zircon. The section shows foliation with mica in 
the centre, quartz on each side, and at top and bottom felspar, in 
the upper part associated with mica. 
Y. Quartzite, Newton Ferrers.—A purplish-grey, hard, crys- 
talline rock. There is a little ferrite between the quartz granules, 
which interlock, and cannot be clearly represented in the micro- 
scope without the aid of polarized light. 
