160 Proceedings of the 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., &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 Roderick 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 feefc 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 



