or certain is, that the moon must
have been nearer, but what proportion that distance bore to the
present distance is necessarily quite uncertain. Some years ago I
delivered a lecture at Birmingham, entitled "A Glimpse through the
Corridors of Time," and in that lecture I threw out the suggestion
that the moon at this primeval epoch may have only been at a small
fraction of its present distance from us, and that consequently
terrific tides may in these days have ravaged the coast. There was a
good deal of discussion on the subject, and while it was universally
admitted that the tides must have been larger in palaeozoic times than
they are at present, yet there was a considerable body of opinion to
the effect that the tides even then may have been only about twice, or
possibly not so much, greater than those tides we have at the present.
What the actual fact may be we have no way of knowing; but it is
interesting to note that even the smallest accession to the tides
would be a valuable factor in the performance of geological work.

For let me recall to your minds a few of the fundamental phenomena of
geology. Those stratified rocks with which we are now concerned have
been chiefly manufactured by deposition of sediment in the ocean.
Rivers, swollen, it may be, by floods, and turbid with a quantity of
material held in suspension, discharge their waters into the sea.
Granting time and quiet, this sediment falls to the bottom; successive
additions are made to its thickness during centuries and thousands of
years, and thus beds are formed which in the course of ages
consolidate into actual rock. In the formation of such beds the tides
will play a part. Into the estuaries at the mouths of rivers the tides
hurry in and hurry out, and especially during spring tides there are
currents which flow with tremendous power; then too, as the waves
batter against the coast they gradually wear away and crumble down the
mightiest cliffs, and waft the sand and mud thus produced to augment
that which has been brought down by the rivers. In this operation also
the tides play a part of conspicuous importance, and where the ebb and
flow is greatest it is obvious that an additional impetus will be
given to the manufacture of stratified rocks. In fact, we may regard
the waters of the globe as a mighty mill, incessantly occupied in
grinding up materials for future strata. The main operating power of
this mill is of course derived from the sun, fo