The answer appears on the ninety-fourth page of the book.

... as for Miss Swartz, the rich woolly-haired mulatto from St. Kitt's, on the day Amelia went away, she was in such a passion of tears that they were obliged to send for Dr. Floss, and half tipsify her with sal volatile

She was burning the midnight oil to finish her part of the project.

The eye unnested from the head, cannot see