The vent at the top of the Menagerie island lighthouse.

(this is the Isle Royale light, not the Rock harbor light that most people see when coming through the Middle island passage)

If you made it to Menagerie island and went inside the lighthouse, climbed the stairs and looked straight up, you would see this. 

Those old lights used a flame and the gases and heat went up and out. 

http://iri.forest.mtu.edu/Lighthouses.htm