SIS l)r Hifcbert m the Distribution 
associated with the quartz, holding a tortuous course so as ge- 
nerally to interrupt the direction of the strata which it tra- 
verses. To show that the associated strata of quartz and horn- 
blende are unconformable with the clay-slate, we must ascertain 
the course of each rock. In tracing the thin strata of quartz 
and hornblende-slate from the south, we find that from Luna- 
bis-ter to Maywick, at which latter place there is an interruption 
to the appearance of these rocks by the sea, also at the Island 
of Trondra where they reappear, the strata, considered collec- 
tively, maintain a course very nearly parallel to that of the clay- 
slate east of them. But at the Vale of Tingwall, the strata 
take a more easterly direction of N. 30° E. to Dale’s Ness 
and the Isle of Glitness. Again, tracing the clay-slate from its 
junction with the sienite to Quarf, we find that little or noj 
deviation is produced in the direction of the clay-slate, but 
that it is nearly conformable to the course of the strata al- 
ready said to be situated to the west of it. But at Scalloway 
a change occurs ; the course of the clay-slate is continued in 
right line, but that of the adjoining strata west of it begins 
to be inflected to the eastward. Hence, there must be an in- 
terception of the strata of clay-slate by the quartz and horn- 
blende-slate ; ^nd, accordingly, a termination of all the rectilinear 
strata, which are thus opposed at their junction by strata cross- 
ing them, may be detected, particularly by observations made 
on the strata of clay-slate north by east from Scalloway. 
The interception of a considerable part of the strata, seems 
to be completed at Dale’s Ness. But, in the bed of Dale’s 
Voe, and on ita j^pestern banks, arises another important mass of 
quartz, associated with hornblende-slate, and nearly in junction 
v/ith the similarly associated rocks which we have traced from 
the south. At Rovie Head, also, situated about a mile to the 
east of Dale’s Voe, arise still other associated strata, consisting 
of quai’tz and limestone, continuous most probably to the Island 
of Greenholm. Lastly, at Kibister’s Ness and south by west 
from it, intermediate to thes^ two masses of Dale’s Voe and Ro- 
vie Head, appear new strata of clay-slate, assuming, however, a 
direction much more to the eastward ; wliich altered direction of 
the clay-slate, considered en masse^ seems connected with the si- 
tuation of the two extri^me masses, the strata of which have a 
