In Ethan Frome, what comparison does Edith Wharton use to show that Mattie brings warmth into an otherwise barren household?

In contrast to the frozen setting of the Frome's
household, Mattie Silver is characterized from her first appearance as an active, warm
and affectionate person. Her arrival is compared to "the lighting of a fire on a cold
hearth" (page 26) and, in contrast to the general stagnation and immobilism of the other
characters, she is described as jumping down from her train with her bundles. On the
following page, the narrator describes several moments in which he supposes Frome felt
closer to Mattie which link her to light and the sun: "the cold red of
sunset behind winter hills", "the flight of cloud-flocks over
slopes of golden stubble, or the intensely blue shadows of hemlocks
on sunlit snow" (27). Mattie's characterization continues with
verbs of movements such as "whirl" and a comparison to "a window that has caught the
sunset" (28).These examples show how Matties is described in
opposition to the stiffness and emotional frigidity that characterizes Ethan and Zeena's
lives.