rtically at one end and one at the other, the single ball being on the
side nearer to the wreck; in fog a gong or bell is rung in quick succession
at intervals not exceeding one minute (wherever practicable); by night,
three white fixed lights are similarly arranged as the balls in daytime,
but the ordinary riding lights are not shown. (18) In narrow waters or in
rivers and harbours under the jurisdiction of local authorities, the same
rules may be adopted, or at discretion, varied as follows:--When a
wreck-marking vessel is used she shall carry a cross-yard on a mast with
two balls by day, placed horizontally not less than 6 nor more than 12 ft.
apart, and by night two lights similarly placed. When a barge or open boat
only is used, a flag or ball may be shown in the daytime. (19) The position
in which the marking vessel is placed with reference to the wreck shall be
at the discretion of the local authority having jurisdiction. A uniform
system by shape has been adopted by the Mersey Dock and Harbour Board, to
assist a mariner by night, and, in addition, where practicable, a uniform
colour; the fairway buoys are specially marked by letter, shape and colour.

[Illustration: FIG. 8.]

[Illustration: FIG. 9.]

[Illustration: FIG. 10.]

[Illustration: FIG. 11.]

British India has practically adopted the British system, United States and
Canada have the same uniform system; in the majority of European maritime
countries and China various uniform systems have been adopted. In Norway
and Russia the compass system is used, the shape, colour and surmountings
of the buoys indicating the compass bearing of the danger from the buoy;
this method is followed in the open sea by Sweden. An international uniform
system of buoyage, although desirable, appears impracticable. Germany
employs yellow buoys to mark boundaries of quarantine stations. The
question of shape versus colour, irrespective of size, is a disputed one;
the shape is a better guide at night and colour in the daytime. All
markings (figs. 8, 9, 10 and 11) should be subordinate to the main colour
of the buoy; the varying backgrounds and atmospheric conditions render the
question a complex one.

[Illustration: FIG. 12.]

[Illustration: FIG. 13.]

[Illustration: FIG. 14.]

London Trinity House buoys are divided into five classes, their use
depending on whether the spot to be marked is in the open sea or otherwise
exposed position, or in a sheltered harbour, or acco