J. pompously instructs the reader to get rid of things they don't need, but his opinions on owning things don’t seem very consistent. In chapter 3, the author employs metaphor, simile, and situational irony to convey J.'s hypocritical perspective on material possessions. As he is frantically packing for the Thames trip, J. laments:
oh, heaviest, maddest lumber of all! – the dread of what will my neighbour think, with luxuries that only cloy, with pleasures that bore, with empty show that, like the criminal’s iron crown of yore, makes to bleed and swoon the aching head that wears it!
Previously J. has referred to material things as "lumber,” useless weight that stops people from achieving their potential. The way he uses this metaphor suggests that material possessions are burdensome and cumbersome, hindering rather than enhancing one's life. The simile he uses here adds to this expression of discontent. He sanctimoniously criticizes the plentiful luxuries and pleasures of his, George’s, and Harris’s life, comparing their “luxury” to a criminal's iron crown. The iron crown is an archaic form of physical punishment which involved tightening a metal band around a wrongdoer's head. As J. says, it "makes to bleed and swoon the aching head that wears it." Having too many material things is a horrible, aching burden, J. implies, and to divest oneself of them all is the only way to be truly free.
Of course, this is full of situational irony, as J. is frantically packing lots of lovely things into bags, and the men consume an enormous amount of luxury goods on their trip. This disingenuous advice just highlights the difference between his words and actions. The irony is further enhanced by the notion that luxury items are “burdens.” J. and his friends are going on a long holiday and have never worried about access to money. Even as he decries it, J. is packing more and more “lumber." The oxymoronic phrases "luxuries that only cloy" and "pleasures that bore" also emphasize the paradoxical nature of having too much luxury. Here, J. is suggesting that what is typically considered desirable and enjoyable can, in fact, become tiresome and unfulfilling. This is another moment where Jerome lampoons middle-class privilege. J. is actually self-pityingly complaining that he can’t enjoy his nice things anymore because he’s too used to them.
J. and George have been sitting in a pub in Wallingford, listening to a series of people earnestly tell them how they caught a famous prize trout that hangs on the wall. Jerome uses situational irony to reveal that the fabled trout is actually made of plaster of Paris:
We thought it strange and unaccountable that a stuffed trout should break up into little pieces like that. And so it would have been strange and unaccountable, if it had been a stuffed trout, but it was not. That trout was plaster of Paris.
The contrast between the expectations set by the stories of the trout's capture and the reality of it being made of plaster is a shock. That contrast is also the source of the situational irony here. J. and George have listened to four different people recount their tales of catching the trout. Each person seems to believe their own story, and each story seems more improbable than the last. The reader, along with the characters, is led to believe that whoever caught it, the trout is a real, stuffed fish.
However, when George accidentally knocks it off its perch, it shatters into pieces, revealing that it is not a real fish at all. Nobody caught it because somebody made it: it’s been crafted from cheap plaster. It then becomes clear that all the stories were fabrications, and the trout was never caught by anyone. The discrepancy between the perceived value of the trout and its actual worthlessness as a plaster replica makes every fishing story about it seem ridiculous.
In the penultimate scene of the novel, Jerome employs situational irony to highlight the characters' self-important hypochondria. The novel ends close to where it starts, with the characters discussing their imaginary ailments:
This naturally led to some pleasant chat about sciatica, fevers, chills, lung diseases, and bronchitis; and Harris said how very awkward it would be if one of us were taken seriously ill in the night, seeing how far away we were from a doctor.
The situational irony in this passage stems from the fact that, on the last night of their adventure, the three men immediately return to enthusiastically talking about their daydreamed illnesses. At the beginning of the novel this was a common topic of discussion. It remains so at the end.
This "pleasant chat" about various ailments is situationally ironic because it contrasts with the expected relief and satisfaction of successfully finishing their journey. Instead of maturely reflecting on their time together, they revert to their habitual self-important grousing. Especially after all the real chaos they’ve encountered, these concerns seem deeply trivial. The irony is further emphasized by the fact that their discussion implies that each thinks his illness is very important and completely unique. None of them are actually ill, but they’re very interested in talking about how unusually afflicted and special they are. This return to the starting point of the novel underscores the fact that Three Men in a Boat is always poking fun at men of leisure. These upper-middle-class people have all the free time in the world, and they choose to spend it diagnosing themselves with deadly diseases.
