Possible Clues:

• Fated never to meet?
• When lines are equidistant and never intersect
• As are lines of latitude
• Of lines, continually at same distance from each other
• Of two lines, continuously at same distance apart
• The 49 th - separates the US from Canada
• Bars having no meeting-place
• Continuously equidistant
• Always the same distance apart
• Like soldier left many times to engage enemy at the front