160 Proceedings of tJie Royal Physical Society. 
masses peculiar to the genus Geodia — all beautiful objects for 
the microscope. A large one, of several pounds weight, con- 
tained pieces of shells, a fragment of an echinus, as well as 
sponge. The flints are slightly waterworn, and many of them 
covered with lichens. With them are blocks of granite and 
gneiss, some of large size, smaller pieces of hornblende, 
reddish conglomerate, quartz, &c.j &c. ; in short, the usual 
heterogeneous collection of travelled stones found in these 
parts. One kind of rock deserves special notice. It is that 
peculiar quartz rock with the large annelide- tubes, so abun- 
dant in the highlands of Assynt, Durness, &c., in Sutherland- 
shire. There is no mistaking it, its character is so obvious. 
For its history see Sir Eoderick Murchison's last edition of 
" Siluria." I would here remark that the north end and west 
side of the small island of Stroma have never been under cul- 
tivation, being too much exposed to the blighting winds and 
burning spray which, when the storm is raging, pass over 
these parts ; and, although some of the cliffs are more than 
100 feet in height, the sea-water at times rushes in streams 
thence to the opposite side of the island. 
I was told by James Simpson, an intelligent fisherman, 
that he had often heard his grandmother say, that in her time 
the supply of peat for fuel for the islanders was cut there, and 
that the moss was then three feet in depth. All has been 
long since taken away, and the scanty vegetation and mould 
which subsequently formed has also been pared off by the 
flaughtering spade, for divots either for the covering of houses, 
&c., or "backing" for fires, and thus the collection of stones 
on this now truly sterile spot is well exposed, and washed 
and bleached by the storms of winter, and the more genial 
showers and sun of summer. These stranger stones, although 
now mingled with others " native and to the manner born," 
show marks which tell of scratching and polishing, move- 
ment and rough usage, after having been torn from their 
native mountains and hills ; and it is interesting to inquire 
into their age, mode of transportation, and deposition there. 
Deposited with the peat they could not be, they date beyond 
that time. The boulder clay period suggests itself, and I 
think correctly ; for although but very slight traces of the 
