he
purpose, that the flow under the railway bridge would have to be much
more considerable than it is at present. In some degree the same
phenomena will be repeated elsewhere around the coast. Simply
multiplying the height of the tide by two would often mean that the
border of land between high and low water would be increased more than
twofold, and that the volume of water alternately poured on the land
and drawn off it would be increased in a still larger proportion. The
velocity of all tidal currents would also be greater than at present,
and as the power of a current of water for transporting solid material
held in suspension increases rapidly with the velocity, so we may
infer that the efficiency of tidal currents as a vehicle for the
transport of comminuted rocks would be greatly increased. It is thus
obvious that tides with a rise and fall double in vertical height of
those which we know at present would add a large increase to their
efficiency as geological agents. Indeed, even were the tides only half
or one-third greater than those we know now, we might reasonably
expect that the manufacture of stratified rocks must have proceeded
more rapidly than at present.

The question then will assume this form. We know that the tides must
have been greater in Cambrian or Laurentian days than they are at
present; so that they were available as a means of assisting other
agents in the stupendous operations of strata manufacture which were
then conducted. This certainly helps us to understand how these
tremendous beds of strata, a dozen miles or more in solid thickness,
were deposited. It seems imperative that for the accomplishment of a
task so mighty, some agents more potent than those with which we are
familiar should be required. The doctrine of tidal evolution has shown
us what those agents were. It only leaves us uninformed as to the
degree in which their mighty capabilities were drawn upon.

It is the property of science as it grows to find its branches more
and more interwoven, and this seems especially true of the two
greatest of all natural sciences--geology and astronomy. With the
beginnings of our earth as a globe in the shape in which we find it
both these sciences are directly concerned. I have here touched upon
another branch in which they illustrate and confirm each other.

As the theory of tidal evolution has shed such a flood of light into
the previously dark history of our earth-moon system, it become