Wernerian Natural History Society. 235 
the strata. The numerous fissures that traverse the sand- 
stone of Arran, and which exhibit every variety of magni- 
tude, direction and dip, afforded apt illustrations of Wer- 
ner’s theory of veins. The porphyry-slate the professor 
described as appearing in the form of overlying conical or 
irregular tabular-shaped masses, resting on the red sand- 
Stone; also in veins traversing granite, sandstone, green- 
stone, and other rocks. He gave a description of some 
“tabular masses of this rock, accompanied by pitchstone 
and claystone, contained between strata of sandstone, and 
which might be confounded with beds, but which he was 
inclined tu consider merely as lateral branches of yeins, or 
as slightly inclined veins. 
At the next meeting, on the 2d of February, Professor 
Jameson read the continuation of his mineralogical obser- 
vations on Arran. He first detailed the geognostic rela- 
tions of the flatx greenstone of that island. From this 
account it appeared to occur in overlying masses resting. . 
on sandstone, in beds in sandstone, and in veins that tra- 
verse sandstone and other rocks. He next described the 
various kinds of pitchstone that occur in Arran, and 
seemed to think that one of the varieties mighit constitute 
a distinct subspecies of the pitchstone species. ‘The ac- 
count of its geognostic relations afforded a detail of many 
curious geognostic appearances ; in particular the structure 
of its veins, and the nature of the interposed tabular 
masses, having many of the characters of beds, yet ap- 
pearing to be either nearly horizontal veins, or lateral 
branches of common veins. ‘The claystone of Arran, 
which was next described, appeared to occur in overlying 
masses, along with porphyry-slate, and also in veins along 
with pitchstone and porphyry-slate. It would seem that 
wacke and basalt are not very frequent or abundant rocks 
in Arran; but when they are observed, they present the 
usual appearances and geognostic relations. 
From the observations in these two memoirs it appears, 
that this island contains no transition rocks; but is prin- 
cipally composed of primitive and fleetz rocks. The ail- 
luvial rocks that occur in the valleys present the usual 
eharacters of the rocks of this class, 
XLII. In- 
