236 ON THE NATURAL HISTORY OF THE SOUTH OF SCOTLAND. 
and Roses in these valleys, in which, as in other respects, they differ essentially 
from the glens of the Grampians. 
The more common direction of the strata in Ettrick is S.W. and N.E., and 
their inclination to the N.W., but both are various. In the vallies of Ettrick 
and Yarrow there are no precipices, nor in fact many exposed portions of rock, 
excepting those in the streams. It is also singular that no rolled blocks are to be 
seen of the diameter of three feet. 
The Ettrick receives the Yarrow below Bowhill, about two miles above 
Selkirk, and their united streams enter the Tweed a mile above Abbotsford, 
where we leave the river to pursue its course towards the ocean. 
Perhaps few districts in Scotland of equal extent present fewer interesting 
geological phenomena than that which contains the sources of the Tweed. Ex¬ 
cepting the limestone at Crook, I have not heard that any of the strata have been 
found to contain organic remains ; nor are such mentioned in any of the Statis¬ 
tical Reports, which, however, are in general extremely deficient in every thing 
that relates to Natural History. 
We have seen that the whole district, so far as it has been examined, is com¬ 
posed of grey-wacke, grey-wacke slate, clay-slate, and slate-clay, passing into 
each other, or alternating, distinctly stratified, often laminar, and frequently 
presenting plates of extreme tenuity. The general direction of the strata is 
from S.W. to N.E. They are usually much inclined, sometimes vertical, and 
not unfrequently horizontal, but present every degree of inclination. The general 
dip is to N.W. 
The composition of the grey-wacke exhibits considerable variety. Sometimes, 
as in the upper part of Eddlestone Water, it is a very closely aggregated frag¬ 
mentary rock, composed of white crystalline quartz, brown and red jasper, black 
Lydian-stone, grey or bluish flinty-slate, and pieces of dark-coloured shale, 
impacted in a fine-grained greyish basis. The fissures are filled with indurated 
argillaceous matter, and dark green unctuous earthy chlorite. Particles of mica 
and felspar are sometimes seen in the mass, of which the aggregation is often less 
perfect when it approaches in character to a conglomerate. 
More frequently, when the rock is large-grained, it is of a bluish-grey colour, 
mottled with white, more* crystalline, but still evidently fragmentary. The basis 
is small-grained, grey, with large fragments of compact or slaty rocks of the 
same colour, or sometimes of dark shale, interspersed. The impacted substances 
are white and grey quartz, with very few fragments of a different colour, some¬ 
times small crystals of calcareous spar, and a few particles of mica. Veins of 
quartz and calcareous spar often intersect this variety. 
From this it passes into a rock presenting at first sight, on its recently-exposed 
surfaces, the appearance of a green-stone, but still composed of the same ingre- 
