in London. Of man there is no record in the
geologic past; but, in the geologic future,
should the race of antiquaries still hold out,
there will be joy in digging for him, and for
all the produce of his hands, now being locked
up carefully beneath the waters of the world.

Some of the lime washed down into the sea
is used by countless animals, who make to
themselves shells. But it is almost certain
that the shells of molluscs and other marine
animals do not grow wholly from this source.
It is more likely that the basis of lime, calcium,
is not an element, although we call it so, until
we know how to resolve it into simpler
forms. Probably it is not an element, and is
produced by the animals from its constituents
existing in sea water. If so, a large part of
the shore of Albion has actually once been
sea; for our chalk cliffs are nothing less
wonderful than the aggregate of myriads on
myriads of microscopic beings, whose remains
have strewed the bottom of the ocean, and
been subsequently lifted up in chalk beds of
amazing thickness.

The ocean is not only a destroyer; it
contributes of its soil to pile up reefs, until they
reach the highest water-mark. It catches
nuts and seeds into its currents, and
industriously scatters them on foreign shores; it
scatters them upon the bald little island, and
there soon grows thereupon a busy crop.
Busy old ocean seizes a canoe, and carries it
upon a current far out of sight of land. "Come
with me, good little men and women," roars
the old fellow, and he shoots them presently
upon the island he has made; and there they
live, perforce, and their descendants people it.
The sea bore no inactive part, assisted by the
trade-wind, in getting over the first ships from
Europe to America. These ocean currents
play, unobtrusively, a large part in the
history of man. But, as Britons, we must
leave ourselves a little time to talk about the
waves, because they are precisely what
"Britannia rules." You know all about the tides,
only as M. Jourdain says of his Latin, we had
better "make as if you didn't." The rise of
tide is caused, of course, by the attractive
forces of the sun and moon, mainly exerted,
as we said, on the south polar reservoir.
There should be two tides to each luminary,
one on its upper and one on its lower transit;
four tides a day; but the attraction of the
lady moon being, as it ought to be, six times
greater than that of the sun, who is a distant
gentleman, she reduces the sun's tide to a
mere supplement. When the gentleman and
lady pull together, then the sun's pull adds
one foot of height to every five feet produced
by the moon, and makes a spring-tide. When
the sun and moon pull in opposite directions,
and the sun wants a high tide where the
moon wants low water, from every six feet of
the moon's tide the sun is able to take one
away, and neap-tides are the consequence.
The varying elevations of the tide at the same
place depending on the varying degree of
unanimity between master and mistress in
the sky.

In different places, however, the height of
the same tide varies considerably—from three
inches to thirty feet. This depends on the
conformation of the land. The great tide
wave, commencing in the Antarctic Ocean, has
its whole course directed by the coast lines.
It flows into the Indian Ocean, where it finds
no northern outlet, and breaks violently on
the shores of Hindostan; rushing into the
ready mouths of the Ganges, it produces the
great bore of the Hoogly. It should flow
into the Pacific, but it finds that ocean
barricaded by innumerable shoals, islands, and
coral reefs; there is no deep, uninterrupted
mass of water, and the tidal movement runs
weakly up the western coast of America,
penetrates not far between New Zealand and
Australia, leaving the shores of China and
Japan, with the great mass of the Pacific
islands, almost wholly unaffected by the tidal
wave. Into the Atlantic it breaks round the
southern point of Africa; the wave that struck
the south shore of New Zealand washes the
Cape fifteen hours afterwards, and passes on
up the Atlantic, touching Africa on one side,
America upon the other. Deflected variously
by the line of coast, after another fifteen hours
of travel, it is ready to come down upon
Cape Clear. Cape Clear and Land's End are
struck by the wave in the next hour, which
then communicates its impulse through the
Irish and St. George's Channels. The rate of
movement of the tide wave depends upon the
nature and depth of the sea bottom. With a
depth of one fathom, its rate is eight miles an
hour, and with one hundred fathoms, eighty
miles an hour; while through deep water of
a thousand fathoms, it is propagated at the
speed of about four miles a minute. Thus the
same wave which touched Cape Clear, passes,
in little more than an hour, on the Atlantic
side to touch the Hebrides, yet takes four
hours in working up the Irish Channel only
to Dublin. So, also, it is a seven hours'
journey for the tide along St. George's Channel
from Land's End to London, which is about
the time it occupied in travelling from Rio
Janeiro to New York. The tide at London
is, however, ruled by the stronger wave
that has rolled round the Orkneys, and
descended thence in about fifteen hours
through the German Ocean to reach London
Bridge, on the third day after its start from
the great southern sea. A glance at the map
will show how small a part of the great tidal
impulse can be communicated to the
Mediterranean through the Straits of Gibraltar;
accordingly, we find a tide of only thirteen
inches on the northern coast of Africa, near
to the Straits, and two, three, four, or five
inches in more protected parts. The Bristol
Channel opens like a funnel, to receive the
full shock of the tide wave entering the Irish
Sea, and there we have a tide of thirty feet.

What we have said about the Crystal Palace