t 
2^6 ' Dr Hibbert mi the Distribution 
I find that it will be difficult under one single term^ to convey 
any significant idea of the ingredients of which the rocks of Re- 
wick Ness and Kirkaness are composed. A white quartz, gene- 
rally compact, is certainly one of the component parts, which is 
the most prevalent ; but this is blended with talc, or with mica, 
w hich approaches much to the character of talc, and also with 
felspar. The term I shall use to express this combination will 
therefore be, a quartzose rock combined with talc, mica, and 
felspar.” The rock is particularly prone to decomposition, so 
that it is difficult to obtain a specimen that is not weathered. 
The stratification is very much confused, and often obscure. 
The best directions which I could obtain were from N. 15* to 
20* E. which is agreeable to the particular course of the strata 
already stated. These also vary much from the interruption 
caused by small insulated masses of granite, as well as by the 
occasional association of the quartzose rock with hornblende- 
slate. Several masses of limestone are also apparent, which 
have a course nearly parallel to that of the strata among which 
they occur ; of these, the most considerable is in the Island of 
Kirkholm. Limestone also occurs at Kirkaness, and on the 
shores of Bixeter Voe. 
To the west of' the quartzose strata at the head of Selie Voe, 
and on its western banks, is a subordinate manifestation of those 
kinds of rocks which I have described under the character of 
nuclei, as affording attachments to strata, as well as determining 
their course and extent. This small bounding mass is a con- 
fused intermixture of hornblende, greenstone, granite, felspar- 
porphyry, and sienite, together with occasional strata of clay- 
slate, the whole being in a very loose state of decomposition. 
This miscellaneous rock has probably, with the exception of the 
clay-slate, the effect of affording attachments to other quartzose 
strata, wffiich, though very considerable as to their extent, may 
be traced north of Bixeter Voe, as far as Aith Voe, in junction 
with the epidotic sienite. 
The Bluish-grey Quartz of Walls and Aithsting,-^ 
This mass may be also, like the granite of Sandsting, consider- 
ed as wedge-shaped, and is best traced from north-east to south- 
west. In a horizontal section, its form seems no less crystal- 
line than that of the granite. Two bounding lines appear to 
