Officer of the Watch. Officer in charge of a watch for the time being.
Official Log. Book in form approved by Dept. of T. & I. issued to Master of a British ship when engaging crew. Is entered with information required by Merchant Shipping Acts concerning such matters as draught of water on sailing, any casualty affecting the vessel, marriages, births, or deaths occurring on board, disciplinary action taken against offenders, particulars regarding boat and other drills, deck cargo carried, etc. At end of voyage is delivered to Superintendent of Marine Mercantile Office.
Offing. Sea area lying between visible horizon and a line midway between horizon and observer on the shore. To keep an offing is to keep a safe distance away from the coast.
Off the Wind. Sailing with wind abaft the beam. Sometimes used to mean being further from wind than justifiable while sailing close-hauled. Said of cowl ventilator when back to wind.
Ohm. Unit of electrical resistance. Equivalent to force of one ampere of current at a pressure of one volt. Standardised as resistance set up in a column of mercury, of uniform diameter, with temperature of 0°C, mass of 14.4521 grammes, length of 106.3 centimetres.
Ohm's Law. Links up relationship between electrical current, voltage, and resistance by formula E = CR when E is voltage, C is current in amperes, and R is resistance in ohms.