Possible Clues:

• Almost identical to king's circumference
• The line 4 is least likely to cross
• Notional line drawn around the earth
• Line dividing the hemispheres
• Continuous line on map's almost identical on rocky peak
• A quote misconstrued by reading circle?
• Line on a globe
• 'Mountains big with mines, / That on the high — ridgy rise' (James Thomson )
• This line's translated for a country it divides
• Circle round earth