Hawthorne uses verbal irony in Chapter 14, while describing Holgrave's observation that Phoebe has become sleepy while listening to his story about Alice Pyncheon:
He now observed that a certain remarkable drowsiness (wholly unlike that with which the reader possibly feels himself affected) had been flung over the senses of his auditress.
The drowsiness Holgrave notices in Phoebe is similar to the mesmeric trance under which Matthew Maule placed Alice in Holgrave's story. Holgrave is realizing that if he so desired, he might be able to manipulate Phoebe to do his bidding, just as Maule once manipulated Alice. He chooses not to, marking himself as morally superior to Maule (who, incidentally, is an ancestor of his).
Hawthorne distinguishes this mesmeric type of drowsiness from "that with which the reader possibly feels himself affected." This comment constitutes verbal irony. What Hawthorne first appears to be saying is that the reader might be falling asleep out of boredom, whereas Phoebe is falling asleep due to the power of Holgrave's storytelling. What the comment actually conveys, however, is the opposite. The reader who has been following along, the comment suggests, should not be bored at all, but should rather be riveted. In fact, Hawthorne use facetious self-deprecation (playfully admitting that the reader might be bored) in order to play off the notion that the reader might, in fact, be in a state exactly like the one Phoebe now finds herself in. He claims outwardly to be just a lowly writer who could never manipulate a reader's mind. By brushing off that possibility, he implicitly raises it as well. The reader is left wondering whether they will ever be able to look away from Hawthorne and the story he has been spinning.
Throughout Chapter 18, the narrator uses verbal irony to describe Judge Pyncheon as if he is merely dozing in Colonel Pyncheon's chair, not dead. For instance, the narrator writes:
Neither would it be seemly in Judge Pyncheon, generally so scrupulous in his attire, to show himself at a dinner table with that crimson stain upon his shirt bosom. By the by, how came it there? It is an ugly sight, at any rate; and the wisest way for the Judge is to button his coat closely over his breast, and, taking his horse and chaise from the livery stable, to make all speed to his own house.
This passage makes it sound as though the Judge has a mysterious red stain on his shirt that he ought to cover up before going home for dinner. The narrator has been cagey about stating explicitly that Judge Pyncheon is dead, but his death has been heavily implied; he has died in the same way as Colonel Pyncheon once did, mysteriously choking on his own blood while sitting in the big chair in the House of the Seven Gables. There is no way this man will be rising from the chair to go to dinner tonight.
But in Chapter 18, the narrator plays dumb. He describes everything the Judge is supposed to be doing instead of sitting in the House of the Seven Gables, and he expresses incredulity that the Judge is neglecting all these tasks. Verbal irony often contributes to humor, but it serves here mainly to create suspense and horror. By acting as though Judge Pyncheon is behaving strangely, and by wondering why on earth he is not getting up for dinner, the narrator encourages the reader to question what is real and what is false and to indulge superstitious fantasies about mistaking live bodies for dead. The reader begins waiting for the Judge to rise from the dead to haunt his relatives, just as Colonel Pyncheon and Matthew Maule have figuratively done for many years. The suspense sets the stage for even more suspense in the next chapter, when neighbors all wonder why Hepzibah is not opening her shop anymore. While life continues like normal outside the house, the reader has a sense that a great horror lurks within. Chapter 19 ends with Phoebe walking into the house. Because of the narrator's verbal irony in Chapter 18, the reader has the sense that she is walking into a trap. The dead body in the house is not an inanimate object; rather, it is lying in wait to jump out at her.