Quick for faces

It is a sorrow to finish a long and very good novel!  Middlemarch, book 8, chapter 81:

Rosamond's eye was quick for faces; she saw that Mrs Casaubon's face looked pale and changed since yesterday, yet gentle, and like the firm softness of her hand.  But Dorothea had counted a little too much on her own strength: the clearness and intensity of her mental action this morning were the continuance of a nervous exaltation which made her frame as dangerously responsive as a bit of finest Venetian crystal; and in looking at Rosamond, she suddenly found her heart swelling, and was unable to speak - all her effort was required to keep back tears.  She succeeded in that, and the emotion only passed over her face like the spirit of a sob; but it added to Rosamond's impression that Mrs Casaubon's state of mind must be something quite different from what she had imagined.