Early on in the novel, when describing to readers the relationship between Jim and his father, Marlow uses a hyperbole, as seen in the following passage:
“I can’t tell you whether Jim knew he was especially ‘fancied,’ but the tone of his references to ‘my Dad’ was calculated to give me a notion that the good old rural dean was about the finest man that ever had been worried by the cares of a large family since the beginning of the world […] ‘He has seen it all in the home papers by this time,’ said Jim. ‘I can never face the poor old chap’.”
The hyperbole here—in which Marlow describes Jim’s father as “the finest man that ever had been worried by the cares of a large family since the beginning of the world”—is meant to communicate the intensity of Jim’s devotion to his father, and it explains why Jim is so afraid of his father reading about his trial (for his decision to abandon the passengers on the Patna) in the “home papers.”
Marlow’s exaggerated language is also an example of verbal irony, as he does not actually believe that Jim’s father is "the finest man […] since the beginning of the world." Rather, he's using sarcasm to gently mock the ways that Marlow idolizes his father. This moment highlights how Jim lives in a fantasy world at times, viewing his father, sailing, and adventure in romantic, unrealistic ways.
When Marlow and Jim are on their way to drop Jim off in Patusan, Marlow describes the characteristics of one of the ship’s crew members using racist hyperbolic language and verbal irony, as seen in the following passage:
“[H]er master, a dapper little half-caste of forty or so, in a blue flannel suit, with lively eyes, his round face the colour of lemon-peel, and with a thin little black moustache drooping on each side of his thick, dark lips, came forward smirking […] His flowing English seemed to be derived from a dictionary compiled by a lunatic.”
The first hyperbole here—in which Marlow describes the man’s face as being “the colour of lemon-peel”—is clearly exaggerated. Marlow’s exaggeration is built on the racist notion that East Asian people have a yellow skin tone. The rest of the description of the sailor’s looks also have a racist edge to them, as he describes the man’s “drooping” “thin little black moustache” and “thick, dark lips.” This imagery rests on stereotypical tropes of Southeast Asian people.
The verbal irony in this passage—in which Marlow describes how the man's “flowing English seemed to be derived from a dictionary compiled by a lunatic”—communicates Marlow’s elitism. This sarcastic description communicates how he looks down on the sailor for not having a command of the English language, despite the fact that he is a non-native speaker. With this moment, Conrad is highlighting how white Europeans like Marlow perpetuate racism in both the ways they treat and talk about members of colonized nations like the sailor in this passage.