the Rocks tf Shetland, 241 
The rocks to the west and north of the central mass of ser- 
pentine have a very complicated distribution. A small mass of 
porphyritic gneiss (if it can be so called, for it shews very little 
of the stratified structure,) may be, in the first place, observed at 
Lambaness, and at the insulated rock named The Scaw. 2dly, 
May be remarked a cuneiform mass of quartz, containing some 
felspar, and occupying a site between Burravoe and the Loch of 
Cliff. 3dly, May be remarked a bed of limestone to the east of 
the Loch of Cliff. 
Now, the space intermediate to the central mass of serpentine, 
the porphyritic gneiss, the limestone and the quartz, is occupied 
by the Hill of Saxivord, consisting of striated strata of mica- 
slate, which are connected with all the bounding rocks that I 
have mentioned, and which meet each of them at various angles. 
With regard to the islands in the channel intermediate to the 
Islands of Unst and Fetlar, they consist of serpentine, diallage, 
and chlorite-slate, shewing that Unst and Fetlar may be con- 
sidered as part of one formation. 
I have at length concluded my account of the distribution of 
the rocks in Shetland, which, although a mere abstract, has 
extended itself to a length that I had not anticipated. In a 
country ofiering so many objects of notice to the geologist, I 
have, through the medium of this Journal, presented those phe- 
nomena only which might tend to throw some light on the nature 
of stratification ; yet the form, distribution, and comparative 
heights of the hills, together with the changes which the rocks 
are in the process of undergoing from various existing causes, 
are distinct subjects of equal interest, to which I have not had 
space to advert. 
The general conclusion from a disposition of rocks like that 
which I have described, is readily suggested. If the resem- 
blance to nuclei which I have endeavoured to trace in the rela- 
tions of certain mountain masses be admitted, then will the gra- 
dual manner in which the rocks at their junction pass into each 
other, assign to the whole of the hills of Shetland a cotempora- 
neous formation. But this opinion I offer with considerable 
diffidence, since the analogies upon which it is founded, do not 
by any means communicate to it the force of a complete induc- 
tion. A number of facts are still required to decide questions 
