1893,] Proceedings of Scientific Societies. 1111 
regarded as an outcrop, as other similar seams or masses are quite 
prominent, interbedded with the sands and gravels. In some places 
coarse gravel and clay nodules are so cemented together with limonite 
that a firm conglomerate is formed. Iron iseverywhere abundant. In 
some hand specimens of the conglomerate may be seen pyrite, magne- 
tite and limonite and spring waters are impregnated with the sulphate- 
Ace tic iron sand may also been seen in places. 
Yellow Gravel or Pre-Glacial Drift is also, to a limited extent, a con- 
stitutent of the assorted material. 
It is evident that only the upper part of the clay has been reached 
and this is very much disturbed and crumpled, portions having been 
torn off from the main mass below, forming the irregular beds or seams 
associated with the sands and gravels. The indications are that these 
were all deposited previous to the advent of the'glacier which shoved 
them ahead and finally left them overlapped by the thin edge and 
flanked on the north by the mass of the bowlder till. 
The character of the clay is not that of our ordinary bowlder clay, 
which is nearly always colored red from the prevailing constitutent— 
eroded Triassic sandstone and shale. These clays are bluish and the 
rock from which they were formed is not anywhere in evidence at the 
present time. The large amount of mica and the occasional fragments 
of mica schist, hornblende schist and granite which are to be found 
throughout all the underlying deposits at Arrochar may perhaps be 
accounted for on the theory ofa belt of such rocks to the south and 
east of the serpentine ridge which has suffered decomposition and ero- 
Sion and thus formed the source of supply for the bluish clay and mica- 
ceous fragments. Such a belt is theoretically present, for we know that 
it exists to the east of the serpentine at Tompkinsville and St. George. 
This theory is emphasized by the position of the clay which is beneath 
and older than the bowlder tilland would thus have been formed inde- 
pendent of material from the red Triassic area which did not suffer 
extensive erosion until it had been overridden by the glacier. One 
lenticular basin of clay in the upper part of the till north of the moral 
nal edge, deserves attention from the fact that the clay there formed is 
typical reddish bowlder clay, horizontally stratified and evidently 
undisturbed since its déposition, which must have been subsequent to 
the retreat of the glacier. This was the source from which the erst- 
while brick yard at Arrochar obtained its material for the manufacture 
of building brick. The comparison between this red, horizontally 
stratified clay in the till above, and the bluish distorted masses beneath is 
striking. : 
