Llandrillo
This,original protraction is formally titled. The traverse routes are noted with the relevant dates and Ordnance Survey field-book page numbers. The conventional sign of a dot within a triangle indicates a trigonometrical point. These appear around the edges of the drawing in red ink,,marking the points from which the surveyor took angular measurements to plot features of the landscape. ,
The British LibraryCollard, Thomas W.
1831