Tide recording gauge consisting of a vertical bronze recording drum with feed and take-up spools for a roll type paper chart. The mechanism is powered by an 8 day mechanical clockwork movement through a set of bevel and standard gears. Mean time is indicated on a standard Roman white enamel dial.
This tide gauge was in use at Richmond lock from 1926 to 1962, the height of tide being recorded on a continuous roll type chart. The gauge is situated immediately downstream of the lock. The water level of the river above the lock is maintained at not less than +5.65 ft. Newlyn Datum, by the operation of sluice gates and the effect of closing these gates on the ebb tide is clearly shown on the tide graph.
The normal patern of the rise and fall of tide at Richmond is that of some 3/4 hrs. flood and 8/9 hrs. ebb. The level of low water is dependent entirely on the amount of land water coming from upstream, and owes almost nothing to the astronomical tide.
Typical tide curve has been drawn on the chart.