BENCHMARKS continued
Perhaps an appropriate way to mark - no pun intended! - the 100th recorded 'mark, is with this one at the Poolbeg Lighthouse in Dublin Bay. Why? Well because the original Ordnance Survey used the low-water mark of the spring tide on the 8th April 1837 at the Poolbeg Lighthouse as a standard height for all its maps, a practice which continued - by the Ordnance Survey of Ireland - up until 1958. The height - for those who are interested - is 20.9 feet on the 25 inch maps, while the original 6 inch maps had it as 21 feet (close enough for jazz), with the high-water mark given as 13 feet. On the visit, Benchmarker (who brought no scuba gear) was unable to spot any trace of either the high or low-water marks that were originally established for these measurements.
Below: The 'mark at the Poolbeg Lighthouse in Dublin Bay. Note that the 'mark is on a horizontal surface whereas most 'marks are on vertical surfaces.
Above: The base of the Poolbeg Lighthouse looking north with the 'mark at left about 1/5th of the way along, and below, the red wall. At right centre is the North Bull Lighthouse, to where Benchmarker will repair presently.