What's the good of Mercator's North Poles and Equators,

⁠Tropics, Zones, and Meridian Lines?"

So the Bellman would cry and the crew would reply

⁠"They are merely conventional signs!

"Other maps are such shapes, with their islands and capes!

⁠But we've got our brave Captain to thank"

(So the crew would protest) "that he's bought us the best—

⁠A perfect and absolute blank!"

This was charming, no doubt but they shortly found out

⁠That the Captain they trusted so well