Page 205 - (DK) Smithsinian - Military History: The Definitive Visual Guide to the Objects of Warfare

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▶ H4 MARINE TIMEKEEPER Index mirror is moved ◀ NAVIGATIONAL SEXTANT
Date 1759 until the sun appears Date c.1770
on the horizon
Origin England Origin England NA VIGA
Material Steel, glass, silver Material Brass
The H4 watch, made by John Jefferys The navigational sextant was used
and based on John Harrison’s design, to measure the angle between the
lost just 5.1 seconds in the course of horizon and the sun or a star.
a two-month voyage from England to The fixed telescope was directed
Jamaica, from November 18, 1761 at the horizon and the radial arm
to January, 1762. moved until the sun or star was TION AND
reflected through mirrors so that
it appeared on the horizon through
the telescope. The angle could be
read off the bottom scale.

Silver case
Telescope is pointed
at horizon COMMUNICA

Calibrated rule

Index bar
moves index mirror TION A

▲ DRAWING TOOLS
Date c.1780 T
Origin England
Material Brass, wood, SEA
leather pouch
Sets of drawing and measuring tools
were used by navigators to plot their
course and draw marine charts.
The tools are contained in a
pouch that could be closed.

Arc measures
one-sixth of circle

Air passes along an elongated
tube called a “gun”

Air resonates in rounded buoy
▲ BOATSWAIN’S CALL ▶ BRITISH NAVAL
Date 1792 SIGNAL FLAGS NUMERIC 1 NUMERIC 2
Origin England Date 1800
Material Silver Origin England
Material Linen
The boatswain’s call was a pipe
used to convey orders aboard ship. Signal flags were used by most navies
Its shrill whistle could be heard for communication at sea, but one of
above the sound of wind and waves. the first efficient, codified systems
A finger was held over the hole to vary was developed by British Admiral Sir
the tone—different combinations of Home Popham in 1800. His system
tone and length of note signaled of numerary flags preceded the
different orders. International Code of Signals, which
was adopted worldwide in 1889.
NUMERIC 4 NUMERIC 9