Quote 157
"I fancy I had some vague notion of falling upon him and giving him a drubbing. I don't know. I had some imbecile thoughts. The knitting old woman with the cat obtruded herself upon my memory as a most improper person to be sitting at the other end of such an affair. I saw a row of pilgrims squirting lead in the air out of Winchesters held to the hip. I thought I would never get back to the steamer, and imagined myself living alone and unarmed in the woods to an advanced age. Such silly things—you know." (3.26)
When Marlow goes chasing after Kurtz, he is confused and has evil thoughts like beating him or "giving him a drubbing" when he finds him. He is confused and certain images burst into his mind. Marlow is concerned mainly with an inevitable sense of catastrophe (which is why he thinks of the old woman who represents Fate) and fear (represented by the pilgrims shooting blindly from their hips).
Quote 158
"Sometimes I ask myself whether I had ever really seen him—whether it was possible to meet such a phenomenon! […]." (3.22)
The harlequin is so hilariously weird that Marlow can't help wondering if he was really real, or if he was just some deranged hallucination of the interior. We have to say, it doesn't seem impossible that Marlow just imagined him.
Quote 159
"He [Kurtz] hated all this, and somehow he couldn't get away. When I had a chance I begged him to try and leave while there was time; I offered to go back with him. And he would say yes, and then he would remain; go off on another ivory hunt; disappear for weeks; forget himself amongst these people - forget himself - you know. 'Why! he's mad,' I said." (3.4)
Even though Kurtz "hates all this," he won't leave it willingly. And that, somehow, is the final clue that Marlow needs to decide that Kurtz is totally crazy. (Really, Marlow? We got there a lot faster than you.)