STRATA of the GRAMPIANS. “9 
dre of a vaft variety of fize, from that of a pea to the bulk of an 
oftrich egg. Thefe are all firmly combined by an argillaceous 
ferruginous cement. In fome parts of this gravel rock, are to 
be feen thin lines of a fine-grained grit, ftretching through-it 
from weft to eaft; it is by thofe lines alone that the vertica- 
lity and the ftretch of this mafs is difcoverable. Its general co- 
lour, in mafs, is that of a ferruginous red. 
Tus plum-pudding rock is immediately followed by a las 
ceffion of ftrata of fine-grained grit, in thin layers: it has a very 
confiderable degree of induration, and is of a dark ferruginous 
brown colour. This deviates alittle from the vertical pofition, and 
inclines to the fouth: the ftretch is from weft to eaft, and its ex- 
tent-towards the north is two hundred and fixty yards. To this 
rock immediately fucceeds a {pecies of Porphyry, the principal 
mais of which confifts of an-indurated argil. Its colour is of a 
purple or lilac brown: its induration is very confiderable, and 
its fracture is rough and earthy. The materials which are im- 
bedded in its mafs, confift of fmall particles of quartz, felfpar, 
blackifh-brown mica, and fpecks of iron ochre ; all of thefe are 
but thinly fcattered. The fpace in the courfe of the river occu- 
pied by this porphyry is two hundred and twenty yards: its 
ftretch is nearly-from weft to eaft, and it inclines in a {mall de- 
gree to the fouth. The rock which fucceeds to this porphyry, 
and which is in contact with it, is difficult to defcribe ; and this 
difficulty arifes from the great diforder of the ftratification, and 
the variety of materials compofing it. The ftrata of this bed do 
not fucceed each other in a regular manner. Portions of them 
of various dimenfions lie together, but very varioufly difpofed : 
fome are vertical, fome horizontal, fome dip to the fouth, one 
only to the north, affording a folitary inftance of a northern in- 
- clination of the ftrata in this field of examination. 
Tue materials of this mafs of confufed ftratification, are of 
very different defcriptions. In one place, a quartzofe ftone 
Voi. VI.—P. I. B abounds, 
