Both Uses of

nonchalant
in
The Mill on the Floss

The neat little lady in mourning, whose light-brown ringlets are falling over the colored embroidery with which her fingers are busy, is of course Lucy Deane; and the fine young man who is leaning down from his chair to snap the scissors in the extremely abbreviated face of the "King Charles" lying on the young lady's feet is no other than Mr. Stephen Guest, whose diamond ring, attar of roses, and air of nonchalant leisure, at twelve o'clock in the day, are the graceful and odoriferous result of the largest oil-mill and the most extensive wharf in St. Ogg's.†
Chpt 6.1

nonchalant = calm and unconcerned

But now she knew that she was about to pass a group of gentlemen, who were standing at the door of the billiard-rooms, and she could not help seeing young Torry step out a little with his glass at his eye, and bow to her with that air of nonchalance which he might have bestowed on a friendly barmaid.†
Chpt 7.2 *

nonchalance = calmness and lack of concern

Definition:

calm in manner -- appearing unconcerned