Harmer's map of glacial erratics and drift, 1928

 

 

Here is the famous map of glacial erratics and drift in England and Wales, first published by the Yorkshire Geological Society in 1928.   Thje map was made by FW Harmer.  For its time, it was very detailed and comprehensive, but like most maps the density of symbols has more to do with the density of research than with the actual distribution of the things being mapped!  Click to enlarge........