_Dates of Maps._--It is very much to be wished that map-makers would always
affix to their maps the date of their execution; the want of this in the
maps of the Society for the Diffusion of Useful Knowledge has often been an
annoyance to me, for it frequently happens that one or both of two maps
including the same district are without date, {397} and when they differ in
some of the minor details, it requires some time and trouble to find, from
other sources, which is the most modern, and therefore likely to be the
most accurate.