Miss CO. A. Raisin—Greenstones & Schists of S. Devon. 267 
gested that this difference, in the results of the transformed augite, 
might be due to an admixture of the constituents of felspar obtained 
in the crushing, either from ophitic plates or from the surrounding 
mass. The felspar in the slide has been completely decomposed, 
and the ophitic plates can be identified mainly by their sharp out- 
lines, preserved within the surrounding augite. Rarely a granular 
crystalline aggregation seems to mark a former felspar now replaced. 
Thus this rock is actually in a condition of transformation, and 
seems to point out what may result from the crushing of an ophitic 
dolerite. Planes of schistosity have been formed, characterized by 
streaks of viridite, probably derived mainly from the pyroxenic 
constituent, and the larger films may mark the loci of what were 
once augite crystals. Secondary hornblende has formed by re- 
crystallization, along the exterior of original crystals, or from the 
shearing, possibly of an unmixed augite. A dusty and granular 
ground-mass, partly kaolinitic, has resulted from the powdering up 
of other constituents, including the greater part of the felspar. 
A slide from rock of a second type is crowded with plagioclase 
felspars, exceptionally well preserved, although they have been 
much broken and snapped by strains acting on the mass. Crystals 
of iron oxide are abundant, some being clearly ilmenite. The 
structure of this rock is difficult to interpret, but the felspars seem 
to have occurred as porphyritic crystals, and not to be pyroclastic. 
Professor Bonney has suggested to me, that the ground-mass might 
be that of a crushed glassy rock, possibly andesitic, and that the 
greenish mineral, which is abundant in it, might perhaps be best 
classed as a variety of palagonite. Mr. Rutley describes and 
figures certain rocks from Cant Hill, near St. Minver, which he 
believes have been derived from what was once a rather basic glass, 
and this slide from Redlap seems to have a ground-mass something 
like that of fig. 1—with broken felspar similar to that of fig. 3.’ 
I have not, however, recognized in these Devonshire specimens the 
vesicular structure, which the other rocks exhibited. 
In a third type of rock, the ground-mass seems to have been 
felspathic, sometimes crowded with well-defined felspars, which are 
now altered to a filmy mineral (? sericite). Porphyritic crystals can 
be traced, which have undergone an aggregate replacement. Other 
groups in the slide, consisting possibly of an intergrowth of quartz 
and felspar, with some calcite, might represent a similar porphyritic 
mineral, or they are possibly amygdaloidal, like that figured by Mr. 
Phillips.?, Sometimes associated with these, but distorted in form, 
are certain viridite or serpentinous strands, which may be examples 
of the crushed amygdaloids noted by Mr. Rutley, or possibly only 
the infilling of secondary cracks. They form the green films, which 
may be noticed on many of the schistose surfaces near Redlap, 
and in my specimens from that locality I searched in vain for any 
of the well-defined chlorite of the southern schists, with which mineral 
1886, vol. xlii. p. 393, pl. xii. figs. 1, 3. 
eGase 
J.G.8. 1878, vol. xxxiv. p. 483, pl. xx. fig. 2. 
