On the errors in longitude as determined by chronometers at sea, arising from the action of the iron in the ships upon the chronometers

• Published in: Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1833
• Subjects: North Pole; South Pole; South pole
• Online Access: http://dx.doi.org/10.1098/rspl.1815.0131; https://royalsocietypublishing.org/doi/pdf/10.1098/rspl.1815.0131

The sudden alterations in the rates of chronometers, when taken on board ships, are generally ascribed to the motion of the vessel; but from circumstances connected with the chronometers of the Dorothea and Trent, during the late voyage to the North Pole, the author is induced to refer these alterations to other causes: he found that in all cases the gaining rates were increased and their losing ones diminished on ship-board. That this acceleration does not arise from the ship’s motion, was shown by its occurrence when the Dorothea and Trent were beset with ice, and when they were at anchor close in shore without any perceptible motion; nor does it appear that change of temperature was at any time the cause of this change of rates. That the iron in ships becomes magnetic is shown by its polarity, the whole forming, as it were, a large magnet, having its south pole on deck and its north pole below. The inner rim of the balance of chronometers, which is made of steel, will, therefore, be liable to magnetic action, which will be sufficient to cause a very sensible alteration in their rate of going. Mr. Fisher concludes this communication with some account of experiments on the action of magnets upon chronometers placed in various positions with respect to their balances, by which it appears that an acceleration in these cases always ensues. It also appears probable, he observes, that the force of the balance spring is affected by the same cause, since chronometers in which they are made of gold, though more difficult to adjust, keep better rates at sea than others.