Used with
permission of Maiken Naylor, University at Buffalo, Buffalo, NY, USA,
http://ublib.buffalo.edu/libraries/units/sel/exhibits/stamps
The zero meridian passing through Greenwich, England, has been used by international agreement since 1884 as the prime meridian for indicating longitude east and west on the earth, a reference for navigators and map makers. These British commemoratives show progressively smaller areas crossed by this imaginary line.