75 
of the Rocks of Shetland. 
Strata supposed to maintain a course from the south-wester- 
ly mass of Epidotic Sienite, until they are intercepted hy the 
Limestone extending from Weesdale Voe to Dalis Voe^ in 
Yell Sound. 
After describing the mass of limestone which intercepts the 
strata to the north, we shall be better prepared to consider the 
relations of the strata both to the epidotic sienite and to the 
limestone. 
Limestone ccmtinuous from Weesdale Voe to Yell Sound. — This 
mass of limestone, of an elongated form, eighteen miles long, and 
about twelve or fourteen hundred feet wide, first makes its ap- 
pearance, as we trace it from the south, in the archipelago of is- 
lands near the mouth of Weesdale Voe. From thence it is con- 
tinued in a direction of nearly N. 12° E. to the head of Weesdale 
Voe, and over a covered country as far north as the head of 01- 
nasfirth Voe. Here the limestone assumes a new direction, being 
inflected considerably to the eastward ; it thus continues in its 
new course to the east of Dale’s Voe, in Yell Sound, disappear- 
ing at length in the peninsula of Foreholm. 
In order to shew the mode by which the strata are intercept- 
ed by those of the limestone, I shall on this occasion consider 
them in an order the reverse of that which I have hitherto 
adopted. This is the order in which they would successively ap- 
pear to us as we cross the strata from west to east, after leaving 
the limestone of Weesdale. 
Strata of Beneness^ and the hill named the Long Kame . — 
These strata are of mica-slate, approaching, however, by the 
slight presence of felspar, to the nature of gneiss. The rock is 
distinguished by the dark colour of its mica. These strata 
may, at the point of Beneness, and the islands of Havery and 
Longa, be observed in the immediate vicinity of the cluster of 
rocks and islands which denote the track of the epidotic sienite. 
At the island of Papa the junction is manifest. Thus there 
can be little doubt, but that the course of the strata is derived from 
the sienite. This course is maintained nearly as far north as the 
head of Olnasfirth Voe, in a direction almost parallel to the course 
of the limestone of Weesdale. But at Olnasfirth Voe, where 
the limestone begins to be inflected in its course to the eastward, 
the lateral edges of the strata of mica-slate, which do not de- 
viate in their line of direction, begin to be successively opposed 
