534 
STRIATION OF ROCK SURFACES ILLUSTRATED. 
same way as glaciers act on the solid rocks over which they are propelled 1 . But 
such a cause, however it may have acted partially, is totally inadequate to explain 
the general striation of the Scandinavian continent. Again, though great waves of 
translation, moving in determinate directions dependent on oscillations of the land, 
may account for the transport of rolled debris to given points, they cannot be alone 
appealed to, as having produced the symmetrical and parallel strise on the surface 
of the rocks. An examination, however, of the former condition of the accumu- 
lations which have been so transported, or in other words, of the nature of the 
bodies which have scratched the rocks, may serve to clear away the obscurity 
which still veils this subject. 
We have already shown, that parallel scratches on the surface of polished rocks 
exist in low tracts at vast distances from mountains, and at the same time have 
stated, that the presence of high mountains behind a glacier is indispensable both 
to the former presence of such a body, and according to experiment and demon- 
stration, to the possibility of its movement. Geologists must, therefore, satisfy 
themselves if there be no other mode of accounting for such polishing and scratch- 
ing, besides the incumbent pressure of moving masses of ice. We in no way 
contend against the value of the explanation of the action of glaciers in Alpine 
regions ; nay, we perfectly subscribe to it, and thank its able expounders for 
having afforded us so good an analogy. We would even make use of the theory 
to enable us better to comprehend, how certain masses which still cover the earth 
and are present to our eyes, in regions where glaciers never can have existed, may 
have yet produced the same results. Let us explain our meaning. In very nu- 
merous countries, whether in low situations, or in those parallels of latitude where 
no permanent ice has been known within the historic period, scratched and polished 
rocks have been observed. Now in all, or nearly all such tracts, we are also aware 
of the prevalence of greater or smaller quantities of drifted detritus. If the tract, 
be rocky and broken up by dislocations, this drift has passed over the shoulders of 
the hills and through the gorges, frequently lodging itself in part upon them, but 
generally having been carried into the adjacent depressions. Captivated by the 
glacial theory, which shows that moraines are the residue of glaciers, some geolo- 
1 Principles of Geology, vol. i. p. 265, fourth edition. See also Mr. Murchison’s Anniversary Addresses 
to the Geological Society of London, Proc. Geol. Soc. vol. iii. p. 686 et seq. and vol. iv. p. 90, in which 
a great many points in the theories of drift and glaciers are discussed, and where it is shown that Mr. P. 
Dobson, of the United States, was the first person who suggested this idea. 
