34 
PROCEEDINGS OF THE PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
teriorated, as there is evidence of floating-ice in the 
Carse - clays, and the clays themselves often closely 
resemble that fine silt or clay which results from the 
grinding-action of glaciers. It is probable, indeed, that 
local glaciers re-appeared in our Highland glens in early 
post-glacial times, and that the Tay and its affluents 
carried down in consequence immense quantities of 
glacial mud, derived from the action of the ice in the 
mountain-districts. The lower flats of alluvium which 
border the Tay, at heights varying from a few feet up to 
two or three yards, show us how, as the sea retreated, the 
river has gradually worked its way down to lower levels. 
Near Glencarse Station a great fault or dislocation of 
the strata is crossed, although there is nothing of it seen at 
the actual surface. This great fracture of the earth’s 
crust passes along the foot of Moncreiffe Hill behind the 
mansion - house, and must cross the Tay somewhere 
opposite Inchyra. It then strikes in the direction of 
Glencarse House, and afterwards runs along the foot of 
the Braes of Gowrie by Kilspindie, Kinnaird, Rossie, &c., 
on towards Lochee. Another great fault occurs in a 
similar position at the foot of the Ochil Hills,—the two 
running approximately parallel. Between these two 
faults the Upper Old Red Sandstone appears at various 
places throughout the Carse, as at Clashbennie, Errol, 
Inchture, and Benvie. 
At Kilspindie the party examined the outcrops of 
ashy conglomerate and porphyrite which are seen at the 
road-side and in the stream-course, Dr Geikie pointing 
out that these represent the oldest visible portion of 
the volcanic series of the Sidlaws. The true igneous 
nature of the porphyrites was seen in their occasional 
slaggy and scoriaceous character,—each individual bed 
being highly cinder-like towards the top, and full of pores 
and flattened cavities below. Some of these little cavities 
were filled with calcite, chalcedony, quartz, agate, &c. 
At the head of Kilspindie Glen a bed of ash-like 
conglomerate is visible. This bed, Dr Geikie said, was 
the lowest of three bands of conglomerate which he 
had traced all along the Braes of Gowrie. Going towards 
Perth, however, the three bands appear to come together 
so as to form one thick mass of conglomerate. It is this 
same conglomerate which underlies the cliff of Kinnoull 
Hill. 
Crossing the hill between Kilspindie and Pitroddie 
Den, the party came upon a thick dyke of basalt, which 
they followed down the hill-slope into Pitroddie Den, 
where it is quarried on a large scale for causeway stones, 
for which it is admirably adapted. The quarries show 
admirably the geological position of the dyke. It runs 
approximately east and west, is about 50 feet thick, and 
dips or is inclined at a high angle towards the south. Dr 
Geikie mentioned that he had seen several dykes of the 
same character in various parts of the same range of hills, 
—one or which could be traced from Fingask Den across 
the wooded hill to the east as far as the turnpike road, on 
the side of which it had been quarried. The Pitroddie 
dyke could be followed up to the head of the Den, beyond 
which its course had not been certainly traced. About 
half-a-mile or so above the quarry the dyke shows a 
curious break. It suddenly dies off on the south side of 
the stream and re-appears on the hill-slope at the opposite 
side at a considerably higher level. It appears to lie for 
some part of its course in the line of a “ fault” or disloca¬ 
tion. 
After examining the thick conglomerate which forms 
the main portion of Oraiglochie Hill, the party pro¬ 
ceeded up the Den, where a series of fine sections display 
a rapid succession of porphyrites and interbedded con¬ 
glomerates,—the porphyrites being ancient lava-flows, and 
the conglomerates representing the gravel and stones 
carried along by torrents and streams. These sections, 
Dr Geikie said, might be considered as typical. From 
them we might gather a pretty good notion of the con¬ 
ditions which obtained during the formation of the 
volcanic series of the Old Red Sandstone formation. The 
porphyrites had been poured out upon the bed of a great 
inland sea in such abundance that the later lava-flows 
were sub-aerial. They formed a long bank or volcanic 
island, down the slopes of which streams and torrents 
made their way to the shores of the ancient sea. One 
could see how the molten rock had now and again over¬ 
flowed the shingle and gravel carried forward by the 
torrents, and caught up many of the stones, which we 
now saw enclosed in the lower portions of the porphyrites. 
Colonel Drummond Hay of Seggieden, than whom no 
one is better acquainted with the Flora of the Carse, acted 
as botanical guide. It is on the “Braes of the Carse,” 
and in the “ dens” which run into the hills, that many of 
the more interesting plants are to be found. It is true 
that in the plain some species occur which are not to be 
found on the braes, but they are for the most part confined 
to the banks of the river, or of the various “ pows ” which 
drain into it. And, considering the high state of cultiva¬ 
tion of the Carse, this is not to be wondered at. 
Among the more interesting plants which were met with, 
or their “stations” indicated (the advanced season of the 
year preventing their being seen in situ), may be mentioned 
the following :—Mimulus guttatus (perhaps a variety of 
the commoner M. luteus), a naturalized American plant, at 
