Overall, the novel's tone is supportive of women and feminine strength, moralizing and paternalistic, and broadly sympathetic to the struggling poor. Throughout, there's also an undercurrent of pathos and melodrama that keeps readers engaged and plays on their sympathies.
The novel uses a strongly admiring tone toward Margaret for her strength and leadership, and by implication, it expresses confidence in women's capacities to bear hardship in general. Throughout the novel, women fare no worse, and in many ways better, than men in the story, especially when it comes to inner, moral strength.
There is also a trace of a hortatory (moralistic) tone regarding the effects of industry on human health and flourishing. Repeated, somewhat melodramatic death scenes (like Bessy's, Boucher's, and Mrs. Hale's) contribute to this tone, and some of Margaret's conversations with Thornton about his responsibilities as an employer encourage readers to adopt a paternalistic outlook—that is, that society's better-off classes bear responsibility for the moral and material well-being of those who are worse-off.
The most pervasive tone is sympathetic, as Gaskell tells the story primarily from Margaret's perspective, in part to give an outsider's point of view on industry's human impact, but also to show Margaret's own strength and capability to care for the suffering. Yet she also writes some sections from Thornton's perspective, humanizing him and the manufacturing class in general. By using this tone consistently, Gaskell refrains from outright condemning any character or group and encourages readers to do the same.