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The average interval between the meridian transit of the moon and the middle of the period of the rise of the tide. It may be computed by adding the half of the duration of rise to the mean low water interval, rejecting the semidiurnal tidal period of 12.42 hours when greater than this amount. The mean rise interval may be either local or Greenwich according to whether it is referred to the local or Greenwich meridian.

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A valve attached to a water column or drum for checking water level.


A vertical tubular member connected at its top and bottom to the steam and water space respectively to a boiler, to which the water gage, gage valves, high and low water alarms and fuel cutoff may be connected.


Test valves on a water column used to verify the water level when the gauge glass is out of service.


One of three valves mounted on a boiler or water column within the visible range of the gauge glass and used to check the water level.


A pipe leading to the bottom of an oil or water tank, for guiding a sounding tape or jointed rod when measuring the depth of liquid in the tank.
Sounding pipes in the engine room are normally fitted with deadweight cocks and screw caps. Caps and cocks should be closed at all times, except when sounding tanks.


The effect that due to the depth of water, the speed of the vessel and shape of the vessel's hull causes the vessel to sink deeper in the water especially in shallow water and at high speed. The vessel becomes sluggish in responding to the rudder.


A caisson having a chamber filled with compressed air at a pressure equal to the pressure of the water outside.


A device for measuring the speed of water currents in which a perforated disk, which rotates with the current by means of a propeller, is placed in the path of a beam of light that is then reflected from a mirror onto a phototube.


A device for obtaining ocean bottom cores up to about 4 feet (1.2 meters) in length; consists of an upper tube, main body weight, and tailfin assembly with a check valve that prevents the flow of water into the upper section and a consequent washing out of the core sample while hoisting the corer.


The highest velocity at which water is permitted to pass through a structure or conduit without excessive damage.

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