How does Mark Twain use imagery in No. 44, The Mysterious Stranger?

Throughout the novella, Twain uses the literary techniques of metaphors and similes such as one in this section that states that sharing ethereal dream thoughts with humans is like "emptying rainbows down a rat-hole." This provides a visual image of the concept instead of merely saying that the dream thoughts are magical and may as well be thrown away if you put them into the heads of mere humans.