Mrs.Bell wondered at this, and on observing that it continued to be so, repeatedly, after several visits, she asked Mary Bell how it happened that Mary Erskine kept her so nice.
"Oh," said Mary Bell, "I always put on my working frock when I go out to Mary Erskine's." The working frock was a plain, loose woolen dress, which Mary Erskine made for Mary Bell, and which Mary Bell, always put on in the morning, whenever she came to the farm.

Her own dress was taken off and laid carefully away upon the bed, under the curtains.

Her shoes and stockings were taken off too, so that she might play in the brook if she pleased, though Mary Erskine told her it was not best to remain in the water long enough to have her feet get very cold.
When Mary Bell was dressed thus in her working frock, she was allowed to play wherever she pleased, so that she enjoyed almost an absolute and unbounded liberty.

And yet there were some restrictions.

She must not go across the brook, for fear that she might get lost in the woods, nor go out of sight of the house in any direction.