42 MR STEVENSON ON THE GEOLOGY OF COCKBURNLAW, 
among these hills. At several localities, series of specimens may be obtained, 
shewing the gradual transition from the unaltered greywacke, to where it becomes 
converted into syenite, which again passes into granite; and the latter, in its 
turn, graduates into porphyry,—the progress of transformation being so gradual, 
as to render it very difficult to decide where the characters of the aqueous rock 
become merged in those of the zgncous. In many cases, the only way of distin- 
guishing the original planes of stratification from those of cleavage, which have 
been superadded in the metamorphic process (unless, indeed, we can trace the 
strata uninterruptedly from where they are unaffected), is by the schists which 
alternate with the greywacke. These are sometimes much contorted, and present 
the appearance of hornblende slates. 
While the greywacke is thus altered, wherever it approaches the granite or 
porphyries, the old red sandstone strata, being of a date subsequent to that of the 
eruption of these older traps, are unchanged even at the place of contact. This 
is seen on the SW. side of the Staneshiel, where the red sandstones are tilted up 
against the granite at high angles, without any appearance of alteration,—the 
granite and overlying sandstones having, in this instance, been elevated (as we 
shall hereafter shew) by the agency of the augitic traps. 
Porphyry of the Knock Hill——tThis rock is of a grey colour, having a felspathic 
basis, and containing a considerable quantity of carbonate of lime. The hill to 
westward of Burnhouses consists of the same rock, and is connected with the 
Knock hill by a ridge running in a SSE. direction. To westward of the felspathic 
mass of the Knock hill, the greywacke appears in nearly vertical strata, with a 
NNW. strike, and is considerably altered by the proximity of the igneous rock, 
being hard and full of quartz veins. On the east side of the hill, and within a 
few feet of the porphyry, the red sandstones are seen tilted up at high angles, and 
even partially retroflexed ; but being of more modern date (as in the case of the 
junction of the granite and sandstones on the west side of the Staneshiel), they 
shew no traces of metamorphism, but remain quite fresh and soft; and the re- 
mains of scales, &c., of the Dendrodus which they contain still preserve their 
original colour. Similar appearances are also observed in the vicinity of the por- 
phyry in Kidshielhaugh. 
2. Augitic Traps. 
Rocks of this class also abound in the form of dykes, beds, and irregular 
masses, and consist of several varieties of greenstone, basalt, amygdaloid, and trap 
tuff. These have all been erupted subsequent to the deposition of the old red 
sandstone and lower coal measures, as is evident from the disturbance and meta- 
morphism apparent in these strata, whenever they approach to traps of this class. 
With one or two exceptions (to be hereafter noticed) they do not appear in con- 
tact with the older rocks, being confined to the secondary strata, which are much 
