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the resistance at the bottom, they become more and more 
parallel to the coast line ; and, where the depth is such that 
the currents would produce any material action on the 
bottom, they could not cut it at an angle of above 30° or 40°. 
Hence, if the wind blew equally in all directions, there would 
be the effects of currents ranging over an angle of double 
that amount, with a mean line perpendicular to the shore, 
and also to the axis of the estuary, if, as is usually the case, 
the shore was more or less closely parallel to it ; whereas if 
the waves came more from one quarter than another, the 
mean line would be inclined from the perpendicular towards 
that side. The rise and ' fall of the tide causes sandbanks 
and shoals to be much elongated in the line of the tide 
currents, and hence the currents due to waves stranding on 
them would also generally be nearly perpendicular to the line 
of oscillation of the tide in the intervening channels ; and 
this^fact enables one to ascertain their position and form in 
ancient deposits. The author described many other peculi- 
arities in the movements of waves, which cannot be well 
explained without numerous illustrations, and he has there- 
fore confined himself in this abstract to some of the most 
important. 
In a paper read before this Society at Huddersfield, 
April 15th, 1852, I showed how the direction of a current, 
present during the deposition of a rock, can be determined 
from the ripple markings, and what I called drift bedding, 
which may be conveniently called " current structures." 
Those produced by the rise and fall of the tide, or by 
stranding waves, are characterised by shewing that the move- 
ment was along a particular line, but first from one side, and 
then from the very opposite, repeated over and over again. 
This line may be determined by taking the mean of the 
separate observations. I usually take a mean for those from 
each side, and, representing them on a map by arrows, show 
