260 PROCEEDINGS OF THE GEOLOGICAL sociETY. (Jan. 5, 
and greywacke in Teviotdale. In this section (Fig. 3), on the Oxmam 
Water, about six miles south-east from Jedburgh, the lowest beds 
are again slate and greywacke, as usual highly inclined. These 
are overlaid by beds of sandstone of a yellow colour with patches of 
reddish brown. Above these is porphyry of a light reddish yellow 
colour, connected with the great mass of this rock im the Cheviot 
mountains. 
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Greywacke. 
The facts just stated are of considerable importance in determining 
the age of the greywacke rocks in the south of Scotland. They are 
thus shown to be of far higher antiquity than the old red sandstone. 
Not only have they been previously deposited, but they have also 
been consolidated and raised up into a great mountain-chain, before 
this more recent deposit began to form around their margin. This 
is evident from the highly inclined position of the greywacke, con- 
trasted with the horizontal, almost undisturbed position of the red 
sandstone, which shows that from the time of the deposition of the 
latter rock, this region has not undergone any very important general 
convulsive action. Indeed many facts would induce us to believe 
that this district had assumed nearly its present physical outline, its 
characteristic ridges of hills and longitudinal valleys, and even that 
the existing rivers were flowing in their present directions, at the time 
when the red sandstone began to be formed. Of these facts I shall 
only mention two. The first is the prolongation of the red sandstone 
in bays, or tongues as it were, up the valleys of the present rivers, 
where they leave the greywacke hills. Had the red sandstone been 
deposited uniformly over a level surface of the slaty rocks, and both 
formations at a more recent period eroded by aqueous agents so as 
to form the present valleys, the features exhibited would have been 
directly the reverse. Promontories of the older rocks would then 
have projected along the valleys into the outline of the newer rocks, 
the higher formations having necessarily undergone the greatest de- 
nudation. The second fact is, the prevalence of coarse conglomerates 
im the red sandstone at the places where the present rivers enter that 
formation ; that is, at the pomts where they formerly fell into the red 
sandstone sea. I have remarked these conglomerates especially on 
the Tweed near Melrose and on the Ale and Teviot. They consist 
of rounded water-worn boulders of the greywacke and felspar rocks 
in a basis of red clays, and closely resemble the debris brought down 
by these streams at the present time. It is, however, right to state, 
that with these boulders of local origin there are others resembling 
the primary strata, and which, differmg from any rocks observed in 
