Angel as simile for good musician
Frank Dunbar says that Philip’s violin will never help the ugly, coarse, rude Nick Holden become popular with the girls “even if he learns to play like an angel”, because Nick’s appearance and mannerisms are too obnoxious to be overcome by musical skill.
Gilpin as a simile for excessive frugality
Because he has saved two hundred dollars, which is a significant amount of money for an eighteen-year-old at the time, Nick Holden can afford to buy Philip’s father’s gold watch when it is put up at auction. But the author compares Nick to Mrs. Gilpin, the author of "Mrs. Gilpin's Frugalities", a popular contemporary book about home economics.
Nick's intentions of self-gratification are thwarted by his excessively frugal nature. He wants the watch, but not enough to buy it for what it is worth. He therefore underbids on the watch and sees it sold to Mr. Dunbar. Nick later tries to manipulate Squire Pope into allowing him to buy Philip's violin for far less than it is worth. This greed sets Nick up as a minor antagonist to Philip.
First-class hotel as a simile for a lavish lifestyle
Joe Tucker is stating that the people who live in his almshouse do not enjoy an excessively high standard of living at the expense of the townspeople. He is speaking truthfully: he feeds his poor residents barely enough to keep them alive and does not spend their food allotment on food for them. However, to deflect attention from this problem, he sets up what is often called a "straw-man" argument. He asserts that his poor residents want and expect lavish accommodations consistent with a first-class hotel, and points out-- rightly-- that it would be inappropriate and irresponsible for him to provide such a lavish lifestyle for indigent people at public expense. The straw-man (in this case the notion that poor people believe they are entitled to luxuries most people cannot afford for themselves) works: it distracts Squire Pope from the real problem and causes him to abandon his investigation.
The fact Squire Pope, an experienced politician, fell for Joe Tucker's straw-man argument and a little bit of flattery reveals that Pope is not as wise or sophisticated as he believes himself to be. This notion is reinforced later in the book when he is manipulated by anybody who knows how to play to his ego.
Incense as simile for something pleasant
Joe Tucker’s flattery of Squire Pope is compared to incense, a fragrant-smelling and pleasant offering generally associated with religious rituals. By using a semi-religious association (which also plays on the name "Pope" which is the title of the head of the Roman Catholic Church), the author suggests that Squire Pope's appetite for flattery is inappropriate and that it is a sinful trait that could easily lead to a form of blasphemy.
Alger, who came from a strong religious background, did not always use his books to promote religion but generally presented religion in a positive and legitimate way.
Tiger as simile for aggression
Joe Tucker blames Philip for the incident in which Philip attacks Zeke to stop him from torturing a small dog, and asks why Philip didn’t simply ask Zeke to stop instead of attacking him “like a tiger”. Philip asserts that he did remonstrate with Zeke, which is a slight exaggeration: all Philip did was ask Zeke what he was doing, relying on his tone of voice to be sufficient criticism.
