the CD version of Manxnotebook actually has a copy of the 1873 1in O/S tiled into 15 'squares' - the base map is the outline map which gives a clear image (the hills map which shades the hills is available as a reprint eg from Museum Shop which has been rectified and overlaid with UK nat grid which makes it easy to tie in with the 2.5in/mile public rights of way map which shows many of the tracks which served as roads prior to the road building of mid to late 18th C.)