Lights shown at the entrance of a harbor, to indicate tide and tidal current conditions within the harbor.
Related Terms 
SEEBECK EFFECT
When two different adjacent metals are heated, an electric current is generated between the metals.

AMMETER
An instrument for measuring the magnitude of electric current flow.

ARC
A flash, caused by an electric current ionizing a gas or vapor.

ALIVE
A term referring to a circuit in which a current is flowing. Also referred to as live.

ALTERNATOR
A device which converts mechanical energy, into alternating current.

HALFTIDE BASIN
A lock of very large size and usually of irregular shape, the gates of which are kept open for several hours after high tide so that vessels may enter as long as there is sufficient depth over the sill. Vessels remain in the halftide basin until the ensuing flood tide before they may pass through the gate to the inner harbor. If entry to the inner harbor is required before this time, water must be admitted to the halftide basin from some external source.

HARMONIC FUNCTION
Any real function that satisfies a certain equation. In its simplest form, as used in tide and tidal current predictions, it is a quantity that varies as the cosine of an angle that increases uniformly with time

HARMONIC FUNCTION
Any real function that satisfies a certain equation. In its simplest form, as used in tide and tidal current predictions, it is a quantity that varies as the cosine of an angle that increases uniformly with time

HARMONIC FUNCTION
Any real function that satisfies a certain equation. In its simplest form, as used in tide and tidal current predictions, it is a quantity that varies as the cosine of an angle that increases uniformly with time

HARMONIC CONSTANTS
The amplitudes and epochs of the harmonic constituents of the tide or tidal current at any place
