This data-set derived from 133 locations in Galicia, north west Spain,
 at which moss samples were taken and assayed for lead-concentrations.

 The three columns of the spread-sheet are:
   x: easting
   y: northing
   z: lead concentration (micrograms per gram dry weight)


 A digital representation of the boundary of Galicia is also available as 
 the file Galicia_boundary.csv