765 
appear to be any reason for doubting that the same law holds for 
much greater velocities. Assuming this law, the author states it 
as the result of a simple calculation, that if a certain current be 
just able to move a block of given weight and form, another cur- 
rent of double the velocity of the former would move a block of a 
similar form, whose weight should be that of the former in the 
ratio of 2°: 1, i.e. of 64 to 1. If the velocity of the second cur- 
rent were treble that of the first, the weights of the two similar 
blocks would be in the ratio 3°: 1, 2, e. of 729 to 1, and so on for 
other velocities. Hence, if a current of ten miles an hour would 
move a block of five tons, a current of twenty miles an hour might, 
under similar circumstances, move one of 320 tons. No transported 
blocks approximating to this weight appear to have been moved 
from the Cumbrian mountains. The author, therefore, does not 
hesitate to affirm the entire adequacy of the cause now explained 
to transport all the erratic blocks which have been identified as be- 
ing derived from that region, nor can he therefore hesitate to -con- 
clude that such has been the agency by which that transport has 
actually been effected. 
It has been urged that no current could carry boulders up the 
escarpment of the Eastern Wolds of Yorkshire, nor does the author 
contend for any such effect of currents. Whether the blocks now 
found on the woids were transported there by currents or by float- 
ing ice, the transport must have taken place before that region 
emerged from the ocean. But the author contends that the forma- 
tion of such an escarpment as that referred to, or like the oolitic 
escarpment which overlooks the valley of the Severn, could not 
possibly be formed by oceanic currents, except under very peculiar 
conditions, which we have no reason to believe to have existed in 
those localities. On the contrary, the formation of such escarp- 
ments during the gradual emergence of the land would be a neces- 
sary consequence of that emergence under conditions which must 
have obtained in numerous instances. Hence the author concludes 
that the escarpment of the wolds was formed subsequently to the 
transport of the blocks which are now found in that region. He 
conceives that, with respect to ‘the theory of transport by currents, 
difficulties founded on existing inequalities of surface have been far 
too strongly contended for on ‘the one hand, and too easily admitted 
on the other. 
The author is anxious that his views should not be nivunaeld 
stood as respects the glacial theory, or that which would refer the 
transport of blocks to floating ice. He is quite prepared to believe 
in the possible extension of glaciers beyond the boundaries to 
which they now extend, wherever such greater extension can be ac- 
counted for consistently with the conclusions of collateral branches 
of physical science; and also to believe that such more extensive 
glaciers, where they have existed, may have been the means of 
transport of erratic blocks, provided sufficient mechanical cause 
can be assigned for their movement. With respect to the iceberg 
