The narrator describes St. Ogg's as an inland town, "which carries the traces of its long growth and history like a millennial tree." We are taken briefly through Roman, Saxon, and Norman times and are told the story of St. Ogg, patron saint of the town. Ogg was a ferryman on the Floss, who ferried a woman and her child across the river Floss one windy night when other ferrymen refused. Upon reaching the other side, the woman revealed herself as the Virgin Mary, sainted Ogg for his pity of her and quick action, and subsequently saved Ogg during one of the historical floods of the river Floss. The history moves on through the civil wars of Puritans and Loyalists and through the changing dynamics of anti- Catholic feeling. At the time of our story, people in St. Ogg's do not spend much time thinking about politics or the long history of the town.
The narrator discusses Mr. and Mrs. Glegg. Mr. Glegg is retired and spends much time in his garden, thinking about natural history as well as "the 'contrariness' of the female mind, as typically exhibited in Mrs. Glegg." Mr. Glegg and Mrs. Glegg are both stingy, though Mr. Glegg is more good-natured in his impulse to save money.
Mr. Glegg goes into breakfast and finds his wife still sullen from the quarrel at the Tullivers and unreceptive when he urges her not to call back the five hundred pounds from them. Mrs. Glegg retreats to her room in a stubborn huff, but changes her mind by the end of the day and decides not to demand the money, chiefly because Mr. Glegg has pointed out potential loss of money trying to find another way to invest it. Mr. and Mrs. Glegg enjoy their evening quarrel-free and discuss the folly of the Tullivers.
Mrs. Pullet arrives at Mrs. Glegg's the following day to discover that Mrs. Glegg has already decided she won't call her money back, and Mrs. Pullet does not need to coax her. Instead, they discuss the poor behavior of the Tulliver children at Mrs. Pullet's and share pessimistic predictions for both Tom's and Maggie's futures. Mrs. Pullet would like to see Maggie sent to a boarding-school.
Before Mrs. Pullet can advance to the Tullivers to announce Mrs. Glegg's amiability in the matter of the loan, a letter arrives from Mr. Tulliver telling Mrs. Glegg that her five hundred pounds will be repaid within the month. Mr. Tulliver had hastily sent the note upon learning that Mrs. Tulliver had sent Mrs. Pullet to plead for him. Mrs. Glegg is insulted and family relations suffer. Mrs. Glegg does not return to the Tulliver's until just before Tom leaves for school in August.
The opening of Chapter XII uses a long history of St. Ogg's to begin forming the long historical and geographical background to the novel. Indeed, St. Ogg's and its anonymous citizens will form almost a character in their own right as the novel begins to focus on Maggie's and Tom's respective coming-of-ages in relation to their community. In addition to her detailed renderings of individual consciousnesses and tendencies, Eliot attentively traces accumulations of cultural and social characteristics that weigh on her characters. This particular description of St. Ogg's indirectly focuses on one of the main dichotomies of Eliot's novel—the traditional versus the changing. As they are described in Chapter XII, the Glegg's certainly fit into the strata of St. Ogg's society that values all that is static and traditional, yet the history of the town itself foregrounds the inevitable movement of change through the region. Part of The Mill on the Floss will concentrate on the diminishment of traditional provincial life in the face of newly materialistic, entrepreneurial forces. The end of Chapter XIII highlights this movement, as Mr. Tulliver must go outside his family structure to borrow five hundred pounds from a client of Lawyer Wakem's. Here Wakem symbolizes these new forces, and Mr. Tulliver must subsume himself to them as part of his "destiny." The ominous reporting of this situation at the end of Chapter XIII, at the end of Book First, points to the importance of Mr. Tulliver's actions to Book First (his name appears in several of the Book First Chapter titles), as well as the importance of these themes of provincialism versus materialistic capitalism to come.
The portrait of Mr. and Mrs. Glegg in Chapter XII further fills out the extensive description of the Dodson women through Book First—as a unified front, but also as distinguished by quirky, detailed differences. One of the themes that unifies the Dodson women, is their respect for, and attention to, the state of death. We have already seen Mrs. Pullet's deep interest in terminal maladies and funerals. This interest is shared by Mrs. Tulliver, if in a more off-hand way, such as her comment to Mr. Tulliver about the family bedsheets back in Chapter II, "An' if you was to die tomorrow, Mr. Tulliver, they're mangled beautiful, an' all ready, an' smell o' lavender as it 'ud be a pleasure to lay 'em out." In Chapters XII and XIII, Mrs. Glegg is described partially in terms of her frequent hypothetical considerations of the state of things after her own (or Mr. Glegg's) death. Death stands as an ideal state for Mrs. Glegg—a time during which true affection can be felt for her husband and when her standing as a respectable member of the community will be vindicated through the generous terms of her will. This reverential desire for the state of death dictates Mrs. Glegg's particular morality, a sense of duty in relation to legacy, instead of living relations. Thus she will not cut Tom and Maggie out of her will in Chapter XIII despite their father's poor behavior.
The discussion between Mrs. Glegg and Mrs. Pullet in Chapter XIII about Maggie's vices serves to emphasize, at the end of Book First, the overwhelming negative pressure that Maggie has faced throughout the first book. Maggie's spontaneous, non-conforming, and imaginative sense of self must continuously run against outside censure of her appearance, behavior, and talents. Only Maggie's father is depicted as loving her unconditionally, but even his love excuses her personality, rather than supporting it.