height above the water level equals the depth
to the ground below it; for example, a
fifteen foot wave breaks over fifteen feet of
water, but five feet breakers are found also
in eight or ten feet water, nine foot breakers
in the sea of a shore thirteen feet deep. Of
the stroke of a breaker the force is
represented by its weight multiplied by its speed.
Breakers at Loch Awe have torn a stone of a
quarter of a ton from the masonry of the
landing-slip. The waves of the German
Ocean broke in two a freestone column
twelve yards high in a place where it was
nearly four yards thick. In a gale at Granton
a stone weighing a ton was picked out of a
wall and thrown upon the beach. A block
of fifty tons weight was moved by the sea at
Barra Head, one of the Hebrides. At
Plymouth Breakwater, so tremendous is the
force of the breakers, that stones weighing
ten or fifteen tons have been taken from
below low water and carried over the top of
the breakwater. By instruments contrived
for the purpose, Mr. Stevenson found the
force of breakers at the Bell Rock Lighthouse
to be a ton and a-half on every foot of
surface, and the force of Atlantic breakers on
the lighthouse at Skerryvore to be not less
than twice as terrible. On the other hand,
at Sunderland, the North and South Beacons,
formed of wood without any support, resist
the breakers of the heaviest gales. So difficult
is it to generalise upon what Smeaton
called "those powers of nature that are
subject to no calculation." At Brighton the
force of breakers during heavy gales was
found by Sir Samuel Brown to be eighty
pounds to a foot upon a cylindrical column
one foot thick.

This, then, is the general character of those
sad sea waves against which breakwaters are
reared for the protection of the seamen on
our coasts. There are three kinds of break-waters now in use: long-slope, upright, and
floating. The old breakwaters of Tyre and
Carthage, Athens and Halicarnassus, in later
history the breakwaters of Venice, Genoa,
Rochelle, and Barcelona, in our day the
breakwaters of Cherbourg, Plymouth, Kingston,
Howth, &c., have been built upon the
long-slope principle. Stone rubble is thrown
into the sea along the line proposed till the
material reaches above high-water springs.
It is left for the action of the sea to define its
form, and when it is fixed at the angle of
repose, the work is faced with rubble or
squared masonry from the low water-mark
upwards. The profile of such a work varies
with its position. Cherbourg breakwater has
on its outer face four distinct slopes between
the top and bottom: one meets the higher
break of the waves, another has the greatest
slope because exposed to the whole battery
of the breakers, a third is between equinoctial
low-water and the point below the surface
where the action of the breaker ceases to be
felt, and the fourth, with least slope, is
beneath the action of the waves. The principle
has failed, and the upper slopes are now being
removed for alteration. The defect of the
whole long-slope principle, Mr. Calver urges,
is that it creates artificially a shallow fore-
shore, and converts a deep sea wave into a
breaker. This attacks the masonry, and
often in a few hours destroys months of
labour. The long-slope breakwater is a
conjuror that can call up a spirit from the vasty
deep only to be its victim. Moreover, the
first burst of the breaker it assists in making
is upon its weakest part—the toe—where
stones lie in an unconnected heap. These
stones are dug out by the water and thrown
up the smooth masonry. When such a breakwater
faces an oblique sea, there is a shoal
formed, as at Cherbourg and elsewhere, only
to be kept under by a large annual outlay.
The breakwater is defective also by reason
of the vacant spaces between stones. Under
the beat of a breaker, air in such holes has an
explosive force. Again, such breakwaters
are at best suited to front only a storm equal
to the strongest that took part in its formation.
Thus Mr. G. Rennie said of Plymouth
breakwater: "If nature has not a stronger
storm than it has hitherto had, it will remain
firm; but if a stronger storm comes, it will
alter again." Cherbourg breakwater was
three times in forty-two years raised above
high water, and as often beaten down again
by the waves, and the use of an upright wall
above low water had to be adopted. Plymouth
breakwater has several times been partly
wrecked. Eighty yards of Howth breakwater
were once destroyed in a north-east
gale; Kingston requires continual repairs.
At Portrush four thousand tons of material
were washed round the pier-head, and formed
into an artificial reef seventy feet long, rising
three feet above low water. For two
centuries annual havoc has been made on the
mole of Algiers. It is said on behalf of the
long-slope breakwater, that it is an imitation
of the beach formed naturally. In form it is
an approach to such an imitation. But on a
beach Nature repairs what she destroys.
The sea breaks with tremendous weight upon
the Chesil bank as well as upon Plymouth
breakwater; but in one case it gives as much
as it takes, in the other it simply destroys
and compels the employment of a large staff
of men, but for whose industry in keeping up
repairs, the breakwater would soon become
a ruin. When it has been made, the long-
slope breakwater is, in fact, to be maintained
only at a constant and considerable yearly
cost.

When the matter was inquired into before
the Harbour of Refuge Commissioners of
eighteen hundred and forty-four, of nineteen
chief men in engineering science who were
called as witnesses, fourteen were decidedly
opposed to a mode of construction which has
been defined as "rude and unscientific, being
a means of procuring the smallest amount