Prof. O. Lapworth—Ballantrae Rocks of South Scotland. 59 
shapes are also well represented. Besides the large crystals, how- 
ever, there are a considerable number of much smaller lath-shaped 
felspars. These are all water-clear, well twinned, and quite fresh as 
to optic qualities. They all extinguish at very small angles. There 
is no sign of any original ferro-magnesian mineral, which is now 
only represented by abundant chlorite. There is much leucoxene; 
but little sphene or rutile. Broken, bent, and optically strained 
crystals are in plenty here as in the other rocks. 
The two rocks of the Castle Cove may have resulted from the 
alteration of either massive or fragmental igneous materials; the 
microscopic study of them does not afford sufficient evidence for 
decision one way or other. But the structure of the rock just 
described seems plainly to show that it was a massive one, its 
numerous larger felspars set in a ground-mass of which the smaller 
lath-shaped crystals formed part. It was probably a basic rock, 
though much of its felspar seems now altered, by dynamic meta- 
morphism, to mere acid forms. 
The main occurrence of altered igneous rock in this district, 
however, is on a very much larger scale than any of those above 
described, and forms, indeed, one of the principal features of the 
coast at some parts of the parish of Tintagel. 
(To be concluded.) 
IJJ.—On tHe Batranrran Rocks or SourH ScorLanD AND THEIR 
Piace in THE UPnanp SEQUENCE. 
By Pror. Cuartes Larworrn, LL.D., F.R.S., F.G.S. 
(With Plate III. and a folding Table extra). 
(Concluded from page 24.) 
Part II.—The Sequence in the Southern Uplands. 
EXT to the metamorphic region of the Northern Highlands 
there is perhaps no area in Britain where the strata have 
been so contorted and convulsed as in the great Lower Paleozoic 
region of the Southern Uplands of Scotland, and it is only by the 
zonal method of stratigraphy that these complexities can ever be 
successfully unravelled. So far as the present results of the appli- 
cation of that method enable us to judge, it appears that, underlying 
all these stratigraphical complexities, there is, in reality, a broad 
tectonic structure of great simplicity. For, if we make exception, 
on the one hand, of the lowest strata (the Ballantrae or Arenig 
rocks), which, as we have seen, only rise to the surface within 
the limits of the Ballantrae district ; and on the other hand of the 
highest formations (Wenlock-Ludlow), which merely skirt the Upland 
plateau upon its north-west and south-west flanks, we find that 
almost the whole of the Lower Paleozoic strata of the Uplands are 
naturally grouped in two grand lithological terranes, viz. (I.) a 
Lower Terrane (Moffat Terrane), including strata ranging from the 
Upper Llandeilo to the Upper Llandovery ; and (II.) an Upper Ter- 
rane (Gala or Queensberry Terrane), embracing strata generally of 
Tarannon age. 
