_The Smalls Lighthouse._--A lighthouse has existed on the Smalls rock,
18½ m. off Milford Haven, since 1776, when an oak pile structure was
erected by Henry Whiteside. The existing structure, after the model of
the second lighthouse on the Bishop Rock, was erected in 1856-1861 by
the Trinity House and is 114 ft. in height from the foundation to the
lantern floor. A new optical apparatus was installed in 1907.
_Minot's Ledge Lighthouse._--The tower, which is 89 ft. in height, is
built of granite upon a reef off Boston Harbor, Mass., and occupied
five years in construction, being completed in 1860 at a cost of
£62,500. The rock just bares at low water. The stones are dovetailed
vertically but not on their horizontal beds in the case of the lower
40 ft. or solid portion of the tower, bonding bolts being substituted
for the horizontal dovetailed joints used in the case of the Wolf and
other English towers. The shape of the tower is a conical frustum.
_Wolf Rock Lighthouse._--This much exposed rock lies midway between
the Scilly Isles and the Lizard Point, and is submerged to the depth
of about 6 ft. at high water. The tower was erected in 1862-1869 (fig.
14). It is 116 ft. 6 in. high, 41 ft. 8 in. diameter at the base,
decreasing to 17 ft. at the top. The walls are 7 ft. 9½ in. thick,
decreasing to 2 ft. 3 in. The shaft is a concave elliptic frustum, and
contains 3296 tons. The lower part of the tower has projecting
scarcements in order to break up the sea.
_Dhu Heartach Rock Lighthouse._--The Dhu Heartach Rock, 35 ft. above
high water, is 14 m. from the island of Mull, which is the nearest
shore. The maximum diameter of the tower (fig. 15), which is of
parabolic outline, is 36 ft., decreasing to 16 ft.; the shaft is solid
for 32 ft. above the rock; the masonry weighs 3115 tons, of which 1810
are contained in the solid part. This tower occupied six years in
erection, and was completed in 1872.
_Great Basses Lighthouse, Ceylon._--The Great Basses lighthouse lies 6
m. from the nearest land. The cylindrical base is 32 ft. in diameter,
above which is a tower 67 ft. 5 in. high and 23 ft. in diameter. The
walls vary in thickness from 5 ft. to 2 ft. The tower, including the
base, contains about 2768 tons. The work was finished in three years,
1870-1873.
_Spectacle Reef Lighthouse, Lake Huron._--This is a structure similar
to that on Minot's ledge, standing on a limestone reef at the northern
end of the lake. The tower (fig. 16) was constructed with a view to
withstanding the effects of ice massing in solid fields thousands of
acres in extent and travelling at considerable velocity. The tower is
in shape the frustum of a cone, 32 ft. in diameter at the base and 93
ft. in height to the coping of the gallery. The focal plane is at a
level of 97 ft. above the base. The lower 34 ft. of the tower is
solid. The work was completed in 1874, having occupied four years. The
cost amounted to approximately £78,000.
_Chicken Rock Lighthouse._--The Chicken Rock lies 1 m. off the Calf of
Man. The curve of the tower, which is 123 ft. 4 in. high, is
hyperbolic, the diameter varying from 42 ft. to 16 ft. The tower is
submerged 5 ft. at high-water springs. The solid part is 32 ft. 6 in.
in height, weighing 2050 tons, the whole weight of the tower being
3557 tons. The walls decrease from 9 ft. 3 in. to 2 ft. 3 in. in
thickness. The work was begun in 1869 and completed in 1874.
_Ar'men Lighthouse._--The masonry tower, erected by the French
Lighthouse Service, on the Ar'men Rock off the western extremity of
the Île de Sein, Finistère, occupied fifteen years in construction
(1867-1881). The rock is of small area, barely uncovered at low water,
and it was therefore found impossible to construct a tower having a
base diameter greater than 24 ft. The focal plane of the light is 94
ft. above high water (fig. 17).
_St George's Reef Lighthouse, California._--This structure consists of
a square pyramidal stone tower rising from the easterly end of an oval
masonry pier, built on a rock to a height of 60 ft. above the water.
The focal plane is at an elevation of 146 ft. above high water. The
site is an exceedingly dangerous one, and the work, which was
completed in 1891, cost approximately £144,000.
_Rattray Head Lighthouse._--This lighthouse was constructed between
the years 1892 and 1895 by the Northern Lighthouse Commissioners upon
the Ron Rock, lying about one-fifth of a mile off Rattray Head,
Aberdeenshire. The focal plane is 91 ft. above high water, the
building being approximately 113 ft. in height. In the tower there is
a fog-horn worked by compressed air.
_Fastnet Lighthouse._--In the year 1895 it was reported to the Irish
Lights Commissioners that the then existing lighthouse on the Fastnet
Rock off the south-west coast of Ireland, which was completed in 1854
and consisted of a circular cast iron tower 86 ft. in height on the
summit of the rock, was considerably undermined. It was subsequently
determined to proceed with the erection of a granite structure of
increased height and founded upon a sound ledge of rock on one side of
the higher, but now considerably undermined. portion of the reef.
This lighthouse tower has its foundation laid near high-water level.
The focal plane is at a level of 158 ft. above high-water mark. The
cost of the structure, which was commenced in 1899 and completed in
1904, was £79,000.
[Illustration: FIG. 13.--Bishop Rock Lighthouse.]
_Beachy Head Lighthouse._--A lighthouse has been erected upon the
foreshore at the foot of Beachy Head, near Eastbourne, to replace the
old structure on the cliff having an elevation of 284 ft. above
high-water mark. Experience proved that the light of the latter was
frequently obscured by banks of mist or fog, while at the lower level
the transparency of the atmosphere was considerably less impaired. The
Trinity House therefore decided in the year 1899 to proceed with the
construction of a granite tower upon the foreshore at a distance of
some 570 ft. from the base of the cliff (fig. 18). The foreshore at
this point consists of chalk, and the selected site just bares at low
water ordinary spring tides. The foundation course was laid at a depth
of 10 ft. below the surface, the area being excavated within a
coffer-dam. The tower, which is 47 ft. in diameter at the base, has an
elevation to the focal plane above high water of 103 ft., or a total
height from foundation course to gallery coping of 123 ft. 6 in. The
lower or solid portion of the tower has its face stones constructed in
vertical offsets or steps in a similar manner to that adopted at the
Wolf Rock and elsewhere. The tower is constructed with a facing of
granite, all the stones being dovetailed in the usual manner. The
hearting of the base is largely composed of concrete. The work was
completed in 1902 and cost £56,000.
_Maplin Lighthouse._--The screw pile lighthouse erected on the Maplin
Sand in the estuary of the river Thames in 1838 is the earliest of its
kind and served as a model for numerous similar structures in various
parts of the world. The piles are nine in number, 5 in. diameter of
solid wrought iron with screws 4 ft. diameter (fig. 19).
_Fowey Rocks Lighthouse, Florida._--This iron structure, which was
begun in 1875 and completed in 1878, stands on the extreme northern
point of the Florida reefs. The height of the tower, which is founded
on wrought iron piles driven 10 ft. into the coral rock, is 110 ft.
from high water to focal plane. The iron openwork pyramidal structure
encloses a plated iron dwelling for the accommodation of the keepers.
The cost of construction amounted to £32,600.
_Alligator Reef Lighthouse, Florida._--This tower is one of the finest
iron sea-swept lighthouse structures in the world. It consists of a
pyramidal iron framework 135 ft. 6 in. in height, standing on the
Florida Reef in 5 ft. of water. The cost of the structure, which is
similar to the Fowey Rocks tower, was £37,000.
_American Shoal Lighthouse, Florida._--This tower (fig. 20) is typical
of the openwork pile structures on the Florida reefs, and was
completed in 1880. The focal plane of the light is at an elevation of
109 ft. above high water.
_Wolf Trap Lighthouse._--This building was erected during the years
1893 and 1894 on Wolf Trap Spit in Chesapeake Bay, near the site of
the old openwork structure which was swept away by ice early in 1893.
The new tower is formed upon a cast iron caisson 30 ft. in diameter
sunk 18 ft. into the sandy bottom. The depth of water on the shoal is
16 ft. at low water. The caisson was filled with concrete, and is
surmounted by a brick superstructure 52 ft. in height from low water
to the focal plane of the light. A somewhat similar structure was
erected in 1885-1887 on the Fourteen Foot Bank in Delaware Bay, at a
cost of £24,700. The foundation in this case was, however, shifting
sand, and the caisson was carried to a greater depth.
_Rothersand Lighthouse._--This lighthouse, off the entrance to the
river Weser (Germany), is a structure of great interest on account of
the difficulties met with in its construction. The tower had to be
founded on a bottom of shifting sand 20 ft. below low water and in a
very exposed situation. Work was begun in May 1881, when attempts were
made to sink an iron caisson under pneumatic pressure. Owing to the
enormous scour removing the sand from one side of the caisson it
tilted to an alarming angle, but eventually it was sunk to a level of
70 ft. below low-water mark. In October of the same year the whole
structure collapsed. Another attempt, made in May 1883, to sink a
caisson of bi-convex shape in plan 47 ft. long, 37 ft. wide and 62 ft.
in height, met with success, and after many difficulties the structure
was sunk to a depth of 73 ft. below low water, the sides being raised
by the addition of iron plating as the caisson sank. The sand was
removed from the interior by suction. Around the caisson foundation
were placed 74,000 cub. yds. of mattress work and stones, the interior
being filled with concrete. Towards the end of 1885 the lighthouse was
completed, at a total cost, including the first attempt, of over
£65,000. The tower is an iron structure in the shape of a concave
elliptic frustum, its base being founded upon the caisson foundation
at about half-tide level (fig. 21). The light is electric, the current
being supplied by cable from the shore. The focal plane is 78 ft.
above high water or 109 ft. from the sand level. The total height from
the foundation of the caisson to the top of the vane is 185 ft.
Other famous wave-swept towers are those at Haulbowline Rock
(Carlingford Lough, Ireland, 1823); Horsburgh (Singapore, 1851); Bayes
d'Olonne (Bay of Biscay, 1861); Hanois (Alderney, 1862); Daedalus
Reef, iron tower (Red Sea, 1863); Alguada Reef (Bay of Bengal, 1865);
Longships (Land's End, 1872); the Prongs (Bombay, 1874); Little Basses
(Ceylon, 1878); the Graves (Boston, U.S.A., 1905); Jument d'Ouessant
(France, 1907); and Roche Bonne (France, building 1910).
[Illustration: FIG. 14.--Wolf Rock.
FIG. 15.--Dhu Heartach.
FIG. 16.--Spectacle Reef.
FIG. 17.--Ar'men.