In "Heart of Darkness" what is the French man of war doing and why does Marlow refer to it as insanity?

The French steamer takes Marlow along the coast of Africa, stopping periodically to land soldiers and customshouse officers. Marlow finds his idleness vexing, and the trip seems vaguely nightmarish to him. At one point, they come across a French man-of-war shelling an apparently uninhabited forested stretch of coast. They finally arrive at the mouth of the Congo River, where Marlow boards another steamship bound for a point thirty miles upriver. The captain of the ship, a young Swede, recognizes Marlow as a seaman and invites him on the bridge. The Swede criticizes the colonial officials and tells Marlow about another Swede who recently hanged himself on his way into the interior.

Explanation: I am not sure but hope this help

an unbound book has no cover; paris is a single man

explanation:

the power of