228 
Dr Hibbert mi the Distrihutlon 
gin. A few of the conglomerate strata next to those of the 
quartz, range with them at a similar angle of 45°. But, cross- 
ing the strata for a distance of a few yards only, they gradually 
acquire an inclination with the horizon of only 10°, and, main- 
taining this position, they are terminated. Now, there is every 
reason to suppose, that the lower edges of the strata of the con- 
glomerate rock, are in contact with the surface formed by the 
upper edges of the strata of quartz, in the manner of other con-, 
glomerate strata formerly described. This change of inclination, 
therefore, from 45*" to 10®, can be satisfactorily accounted for, on 
the supposition, that the strata had acquired an addition of new 
matter in their descent ; which addition may either consist in an 
increased thickness of the strata, or in an accession of new strata. 
It is thus that the increased accumulation of matter, which the 
strata may possibly have received in proportion to their depth, 
would produce an elevation of the uppermost strata. 
^thly. The Strata maintainmg a Course from the Granite of 
Sandsting to the Bluish-grey Quartz of Walls and Aithsting . — 
An angular space, formed by the easterly bounding line of the 
granite, which obliquely meets that of the quartz, is distinguish- 
ed by the presence of gneiss. This space includes the land to 
the west of Selie Voe, with the exception of Bewick Ness, and 
also the land to the north-west of Selie Voe, and south of Bixetei* 
Voe ; together with that tract which lies between the north of 
Bixeter Voe and the small hill of Braewick, to the west of Aith 
Voe. 
These strata are first observed on an eminence to the west of 
Selie Voe, where they are separated from the quartzose strata 
of Kirkaness, by the intervention of the miscellaneous rock al- 
ready described, which is of little extent, consisting of horn- 
blende, greenstone, granite, felspar-porphyry, and sienite ; to- 
gether with occasional strata of clay-slate. The rocks in all the 
track south of Bixeter Voe, are so concealed by a deep bed of 
turf, that we must depend upon a very few occasional expo- 
sures for the removal of our difficulties with regard to the na- 
ture of the strata. But to the north of Bixeter Voe, and to the 
w^est of Aith Voe, the rocks aie somewhat better exposed. The 
gneiss is occasionally associated with midi-slatc, and is traversed 
by insulated veins of granite. Vrom the very few opportunities 
