On the Fossils of a Boulder-clay in Caithness. 39 
Caithness, run north and south, with deviations to the east 
and west. I have found them almost all over the county. 
Beds of sand occur in some localities over the clay, and 
nests of sand are occasionally in it. Cracks, varying from 
an inch to a foot across, run down the clay to great depths, 
some vertically, others diagonally, and from these run, hori- 
zontally, smaller ones ; all these are filled with sand. The 
sand contained in them was evidently poured in from 
above, first trickling down the sides mixed with tenacious 
matter, and which has consolidated there, the centre of the 
cracks being filled with loose sand. The shells in the sand 
are of the same kind as those in the clay, but so friable, that 
on attempting to remove them, they fall in pieces — thus 
showing that sand is a bad preservative of organisms em- 
bedded in it. 
In many cases where thick beds of sand occur, clay again 
overlies it, and above all, beds of stones of all kinds and 
sizes, which no doubt were left by the after washings to 
which the clay had been subjected, the clay being carried 
away to other localities, and in all probability forms the 
brick-clay, which is said to be younger than the boulder-clay. 
At Pulteney Town, near the harbour, a large block of 
granite, many tons in weight, rests on the Boulder-clay, 66 
feet above the level of the sea. All over the county large 
boulders are met with. The march of improvement is de- 
stroying them fast. The largest I know is at Keiss, Wick, 
a conglomerate block ; its cyclopean size makes it a con- 
spicuous object in the flat field near the farm-house of 
Kilmster. All the clays of Caithness, or nearly so, might 
be made into bricks, tiles, &c. ; it, however, would be rather 
expensive to take out the stones. This could be done by 
washing when preparing the clay for use. A similar clay 
is so treated at Peterhead, Aberdeenshire ; the wares made 
from it are highly prized, and it has been worked profitably 
for 3^ears. In this clay- work I have found similar shells to 
those of Caithness, but much more comminuted, and in less 
abundance. It is also very full of stones. 
Some of the Caithness shells are almost perfect, especially 
the smaller ones ; others, again, for instance the Astartes, 
