354 WR. TATE ON POLISHED AND SCRATCED ROCKS, 
broken state, but others in a perfect condition, showing that 
the animals had lived and died on the spot where they le en- 
tombed. Professor Edward Forbes reckons the total number 
of species of mollusks, found in these beds in the British Islands, 
to be 124: all are marine; and the general facies of the assemblage, 
and some particularly distinctive species, evidence that the fauna 
of this ancient sea was of a sub-arctic character. The researches 
of Sir Charles Lyell, Sir R. Murchison, and others show that the 
boulder formation extended over the greater part of Northern 
Europe, as far down as the 40th degree of latitude, and that a 
similar formation, in North America, extended 10 degrees nearer 
to the Equator. 
Mr. W. J. Carr, who examined the Hawkhill quarry along with 
myself, informs me that the polishing and scratching of the rocks 
there are the same as what he has seen in the Alps, produced by 
glacial action. It is therefore necessary to consider whether ancient 
glaciers may not have protruded from some neighbouring moun- 
tains, and by their motion and weight polished and scratched the 
rocksoverwhich they passed, and moreover transported large blocks 
from the higher regions to the valleys. The distinct indications of 
successive deposit under water, throughout the whole series of beds 
already referred to, appears to me conclusive against the former ex-_ 
istence of glaciers in this district. Nor could glacial action have 
taken place with the present physical conformation of the country ; 
for there are neither high mountains rising above the line of per- 
petual snow, nor vallies with sufficient inclination down which 
the frozen river could be impelled onward. There is a more fatal 
objection ; the Cheviot and Lammermuir Hills are the highest in 
the district, and these are the only ones from which, supposing 
the outline of country had been so altered as to admit of glacial 
action, from which glaciers could have descended ; but that no 
glaciers protruded either from the Cheviots or the Lammermuirs 
is evident from the mineral character of the boulder rocks. The 
Cheviots are porphyry, the Lammermuirs are greywacke ; but no 
large blocks of porphyry nor of greywacke are to be seen in the 
boulder clay ; in the gravel beds rounded porphyry pebbles are 
common, but they are obviously water-worn ; angular blocks of 
