This section of the novel is actually deeply symbolically revealing about Silas's character and likewise the child that he finds. He discovers the child on his doorstep in Chapter 12. We are told that after the robbery of his gold he had developed the habit of opening his door and looking out, as if expecting his gold to come back. However, this time, when he returns from doing this, he sits down, facing the hearth and he seems for a moment to see gold on his fireside hearth:
Gold! --his own gold--brought back to him as mysteriously as it had been taken away! He felt his heart begin to beat violently, and for a few moments he was unable to stretch out his hand and grasp the restored treasure. The heap of gold seemed to glow and get larger beneath his agitated gaze. He leaned forward at last, and stretched forth his hand; but instead of the hard coin with the familiar resisting outline, his fingers encountered soft warm curls.
So we have a very interesting way in which Silas discovers the child of Molly. One could say that his greed for gold confuses the blonde hair with his money, or equally we could argue that George Elliot is actually showing how this young babe will become just as precious to Silas as his gold was before.