To know one's longitude at sea, one needs to know what time it is aboard ship and also the time at the home port or another place of known longitude-at that very same moment. The two clock times enable the navigator to convert the hour difference into geographical separation. Since the earth takes 24 hours to revolve 360 degrees, one hour marks 1/24 of a revolution or 15 degrees. And so each hour's time difference between the ship and starting point marks a progress of fifteen degrees of longitude to the east or west. Every day at sea, when the navigator resets his ships clock to local noon when the sun reaches its highest point in the sky, and then consults the home port clock, every hour's discrepancy between them translates into another fifteen degrees of longitude. One degree of longitude equals four minutes of time the world over, although in terms of distance, one degree shrinks from 60 nautical miles at the Equator to virtually nothing at the poles. Precise knowledge of the hour in two different places at once - a longitude prerequisite so easily accessible today from any pair of cheap wristwatches - was utterly unattainable up to and including the era of pendulum clocks. On the deck of a rolling ship such clocks would slow down, or speed up, or stop running altogether. Normal changes of temperature encountered en route from a cold country of origin to a tropical trade zone thinned or thickened a clocks lubricating oil and made its metal parts expand or contract with equally disastrous results. A rise or fall in barometer pressure, or the subtle variations in the Earth's gravity from one latitude to another, could also cause a clock to gain or lose time.
 SHIPS CLOCK ENGINE ROOM CLOCK  £42.00
|
 BRASS SHIPS PORTHOLE CLOCK SOLID BRASS SMALL NEW £59.99
|
 US MARITIME COMISSION 30 HARDWOOD SHIPS WHEEL WITH BRASS CLOCK not working £85.44
|
 PERSONALISED PIRATE SHIP WALL CLOCK £7.99
|
 SMALL NOVELTY BRASS CLOCK SHAPED AS A CLOCK ON A SHIPS SAIL £11.99
|
 Vintage Ship Boat Engine Room Brass Clock Barometer MUST SEE £14.50
|
 Vintage Seth Thomas Marine Brass Ships Bell Clock strong running clock £96.56
|
 Ships Style Clock Barometer Wood Look Brand New £33.99
|
 RUSSIAN MARINE CLOCK FOR SHIP OR SUBMARINE £54.45
|
 BRASS SHIPS BELL CLOCK £149.99
|
 Vintage marine Sailors Ships wooden Wheel Design wall Clock maritime nautical £4.99
|
 SALE ANTIQUE WHITE MARBLE CLOCK Free Domestic Shipping £6,196.90
|
