ON THE MARGIN OF LOCH LOMOND. 335 
One of these marine deposites was about eight or ten feet 
above the highest level of the present waters. It lay in a 
small hollow, under a projecting precipice of limestonej 
close to the margin of the lake. The only remains of it now 
are some fragments of a very compact calc-tufF, contain- 
ing sea-shells disseminated through it. The limestone-rock 
is now quarried ; and the calc-tuff being the most accessible 
and richest limestone, was first carried off for use. The 
shells appear to have been accumulated in a situation ex- 
posed to the stalactite droppings from the lime-rock, Iri 
the interior of the tuifa, they are chiefly the Mytilus edulis, 
or its congeners ; but the surface is sprinkled with imbed- 
ded specimens, belonging to the genera Planorbis and Helix, 
which have accidentally fallen upon it. This quarry is on 
the east side of the lake, about two miles north-west from 
the mouth of the Endrick, and on the north side of the 
great range of islands composed of Secondary Conglomeratej 
which stretches across the southern end of the lake. This 
limestone is on the lands of his Grace the Duke of Mon- 
trose, and is worked for his tenantry, but is not much 
esteemed for agricultural purposes. It is highly crystalline 
in its fracture, appearing to be irregular layers of crystals^ 
separated by quartz and clay. 
There are other two places, which afford shells, in very 
different circumstances. Those points are similar in situa- 
tion ; both are in slight bays opening to the north, and 
presenting a steep gravelly beach to the water; One of 
them is on the island Inch Lonach, opposite to the village 
of Luss ; and the other, on the lands of H. Macdonald 
Buchanan, Esq., near the south-east angle of the lake: 
The shells begin to appear about half-way between the 
highest and lowest, or the winter and summer, surfaces of 
the water, which varies in this respect about six feet. After 
removing a slight covering of coarse gravel, we find a thiiV 
z 2 
