Find the plaque here commemorating the History of the area, on the reverse side of the rock, there is another plaque with a number in brackets, use this number to get the co-ords to the final (just the last 3 )--add all the digits together and use this sum as follows---
SOUTH--sum x third digit minus three, with the result subtract that off 390
EAST--sum x 2 + 4, subtract that off 259
CHEKSUM---all the 6 digits obtained should add up to 15