Marine Chronometer

George Margetts (1748 – 1808) was an English clock maker who made a wide variety of clocks, such as chronometers, watches, astronomical dials, and astronomical regulators.²² He was also a mathematician who contributed tables to aid in finding longitude by the lunar method.¹⁵ A method which has been discussed in this exhibition. This Margetts marine chronometer has several characteristics that point to a former life on a ship. Its size, along with the handles, would have allowed the clock to be moved by one individual seaman. This portability would have allowed the clock to easily be moved to a dedicated room on the ship for chronometers, but it also would have made it easier to carry on to land to use in tent observatories. The clock itself is mounted on a metal ring attached to gimbals. This allows the clock to sway in a 12-6-12 direction, thereby dampening the effects of a rocking ship by allowing it to move. The inside of the box is lined with a felt material, presumably to reduce vibrations encountered on a moving ship. The keyhole on the front of the box is to lock and unlock the lid. This lid would have served as an added barrier to the extreme elements on a ship to protect the timepiece. There is one key that comes with the box, and this may have been both used for the lid, as well as for the winding mechanism, which is found just under the 3 o’clock region of the clock. Mechanical clocks of this nature need to be wound to provide the stored energy needed to run. Considering this is an 8-day marine chronometer¹⁵, it would need to be wound about once a week.

Despite the seemingly impeccable condition of a chronometer that was most likely used on a ship for many years, and which is over 200 years old in total, the chronometer and its box show signs of having been fixed many times as described in the book Study, Measure, Experiment: Stories of Scientific Instruments at Dartmouth College by David Pantalony, Richard L. Kremer, and Francis J. Manasek (2005).¹⁵ It is this fact that reveals the hidden and contrasting nature of such a precision timepiece. On the one hand, it is a great example of human ingenuity, allowing navigators to conquer longitude—a problem that plagued seamen for centuries. On the other hand, the erosion of such a precision piece—a piece whose construction included enormous sums of money, many minds, and the backing of entire countries—reveals the underlying imperial dimensions surrounding it, as well as the toll that individuals, such as John Harrison, faced in its construction.