1. The difference between the theoretical distance traveled per revolution of a vessel's propeller and the actual advance of the vessel. 2. The motion of the center of resistance of the float of a paddle wheel or the blade of an oar through the water horizontally. 3. The difference between a vessel's actual speed and the speed it would have if the propelling instrument acted upon a solid. 4. The velocity relative to still water of the backward current of water produced by the propeller. 5. A memorandum of the particulars of a risk for which a policy is to be executed, usually bearing the broker's name and initiated by the underwriters.

Related Terms


When two different adjacent metals are heated, an electric current is generated between the metals.


An instrument for measuring the magnitude of electric current flow.


An instrument for measuring the magnitude of electric current flow.


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


An instrument for determining either the specific gravity of a liquid or the API gravity.


Additive for protecting lubricated metal surfaces against chemical attack by water or other contaminants. There are several types of corrosion inhibitors. Polar compounds wet the metal surface preferentially, protecting it with a film of oil. Other compounds may absorb water by incorporating it in a water-in-oil emulsion so that only the oil touches the metal surface. Another type of corrosion inhibitor combines chemically with the metal to present a non- reactive surface.


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


The ability of a fluid that is insoluble in water to separate from water with which it may be mixed in the form of an emulsion.


A device which converts mechanical energy, into alternating current.


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 half-tide 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 half-tide basin from some external source.

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