# File lib/eymiha/units/units.rb, line 50
    def Units.derive(name, target, &block)
      measure = ( @@measures[name.to_s] =
                  if target.kind_of? UnitsMeasure
                    if target.derived &&
                        (derived = find_by_derivation target.derived)
                      derived
                    else
                      target
                    end
                  else
                    Units.create(target.to_s)
                  end )
      block.call measure if block_given?
      measure
    end