Nice shots on the Saguenay. Please note that this vessel did not have a conning tower.
These "towers" should be the ones just forward of each funnel (2 of). The tower(s) would support "risers", pipes that would vent fuel tanks. Each riser should have a bell shaped valve at the end. As the temperature of the fuel changes (sailing in tropics vs. sailing in the north Atlantic), these valves would open and close to avoid excessive pressue and vacuum in the fuel tanks.