of tlie Rochs of Shetland. 
evident where a partial separation has occurred. This space is 
occupied by strata, and is bounded on the N. and W. by the gra- 
nite, and on the south the presence of the granite is indicated 
by the insulated rock of the Drongs : it is bounded on the east 
by the sienitic greenstone. Thus, certain strata, forming an 
area of a mile and a half in length, and three quarters of a mile 
in breadth, appear to be inclosed on all sides by two unstratified 
rocks. These strata, constituting Hillswick Ness, exhibit a va- 
riety of directions, the most prevalent being nearly from west 
by south to east by north. The dip and angle are too confused 
to be stated with any degree of accuracy. This curious assem- 
blage of rocks, in crossing them from north to south, are found 
to be arranged in the following order, viz. quartz, hornbjendic 
gneiss, mica-slate, chlorite, and hornblendic gneiss. They are, 
at the same time, traversed by veins of felspar-porphyry and by 
greenstone. Here also is found steatite, talc, chlorite contain- 
ing magnetic ironstone, cyanite, and actynolite. 
Two series of strata are arranged to the east of the sienitic 
greenstone. To determine the situation and circumstances of 
the first series, it is necessary to refer to a space in the annexed 
geological map, bounded on the east by a mass of sienite, to be 
traced from Hagrasetter Voe to Glus Island, and on the west by 
the sienitic greenstone, the limits of which have been stated. This 
is occupied by strata running in a direction of N. by W. from 
one mass of sienite to the other, and meeting each by their late- 
ral edges at various angles, with an inclination to the east. 
These rocks, which are much concealed by the covered state of 
the ground, appear to consist of hornblendic gneiss and chlo- 
rite, with an enclosed mass of limestone. 
More northerly, a 2d series, continuous with the first, takes 
a course of N. 20'’ E. These strata form the Falling Hill and 
Ollaberry Hill ; and as we cross them from west to east, appear 
to consist of hornblendic gneiss, with an intersecting mass of ser- 
pentine, mica-slate, chlorite, and quartz. Of these rocks, the 
more westerly, consisting of hornblendic gneiss with the serpen- 
tine, of quartz and mica-slate, are intercepted by the granite 
which occurs to the north of Colafirth Voe. The rest of the 
strata are continued northerly, the quartz being finally lost by 
the inroads of the sea at Calsta Ness ; whilst the chlorite-slate 
