W.C. It consists of a drum about 5 in diameter and 10 in high,
which revolves by clockwork once in twenty-four hours, the same
mechanism also driving a small clock. A diagram paper divided
with vertical lines into twenty-four primary spaces for the
hours is fastened round the drum and a pen or pencil attached
to a slide actuated by a rack or toothed wheel is free to work
vertically up and down against the drum. A pinion working in
this rack or wheel is connected with a pulley over which a
flexible copper wire passes through the bottom of the case
containing the gauge to a spherical copper float, 8 inches
diameter, which rises and falls with the tide, so that every
movement of the tide is reproduced moment by moment upon the
chart as it revokes. The instrument is enclosed in an ebonized
cabinet, having glazed doors in front and at both sides, giving
convenient access to all parts. Inasmuch as the height and the
time of the tide vary every day, it is practicable to read
three days' tides on one chart, instead changing it every day.
When the diagrams are taken of, the lines representing the
water levels should be traced on to a continuous strip of
tracing linen, so that the variations can be seen at a glance
extra lines should be drawn, on the tracing showing the time at
which the changes of the moon occur.

Fig. 5 is a reproduction to a small scale of actual records
taken over a period of eighteen days, which shows true
appearance of the diagrams when traced on the continuous strip.


These observations show very little difference between the
spring and neap tides, and are interesting as indicating the