Look at the oil painting. Here it takes much less effort to imagine a mother child silhouette. In fact, you should simply see it.
Homer modified Nature. What was only suggested by Nature, as seen in the sketch, was "improved" by Winslow Homer. Homer followed Coleridge's description of Allston. Homer took "the will for the deed. The great artist does that which nature would do, if only the disturbing forces were abstracted."