Elizabeth Gaskell's Mary Barton provides an in-depth look at the class structure of Victorian England. Gaskell underscores the large gap between the rich and the poor and the fact that there was little room for social mobility. Everyone had a place in society, and it was rare for one to be able to overcome the status they were born into.

Job Legh is an intelligent, self-educated naturalist who keeps his home stocked with books and scientific instruments. His wisdom and intellectual curiosity make him different than most of the other working-class characters in the text and go against the traditional expectations for his social class. Through Legh, Gaskell attempts to show middle- and upper-class readers that working-class people are just capable and interested in being educated as they are. In doing so, she hopes to cultivate more compassion toward the working class so that they can struggle less despite the rigid social structure.

Legh himself even speaks this message directly in the text. Consider how he speaks to Mr. Carson about John Barton's motives. Legh says that when God gives a blessing, "He gives it with a duty to be done; the duty of the happy is to help the suffering bear their woe." Here, Legh reinforces Gaskell's point that the negative effects of social inequality can be addressed through showing the working class compassion.