The incalculable contribution John Harrison made to navigation science, by proving that precision timekeeping was the most practical method of determining longitude, has been written about in earlier blogs, under History of Science. The plans to display the John Harrison clock in the Leeds collections, the clock on which Harrison began his precision timekeeping research in response to the Longitude Act of 1714, are moving forward. Appropriately this new permanent display will be adjacent to the World View gallery. One of the features of the display, recently commissioned, and its manufacture under way, is a circular tablet, one metre in diameter that will be let flush into the floor adjacent to the showcase. It has been designed by the project team and it is being made in the marquetry technique by Jack Metcalfe. It will mark the longitude and latitude of its location, and the points of the compass. The line of longitude, or meridian, will be formed of a bar of brass and steel, like a bimetallic strip, one of Harrison’s most significant inventions.
The grain of the oak veneer is aligned radially, like the oak cogs of Harrison’s early clocks. The centre will be a disc of lignum vitae, a wood he used for friction reduction. The points of the compass will be formed in a black-coloured wood, as will be the longitude and latitude numbers. The font is called Caslon and was in common usage during the 18th century. The meridian line and line of latitude will, of course, run through the centre of the disc. The entire disc will be protected by toughed glass, and be flush to the floor.
|Floor tablet completed, awaiting the stage of display development
when it can be installed.
|Floor tablet installation|
|Installations continue, LMG’s Harrison precision pendulum
clock No. 2 due for installation shortly, to the left of copy movement
borrowed from the National Maritime Museum.