Dickinson uses landscape and place as a background to show the effects of a sunset as it gradually descends from a mountaintop to church steeples, to the grass (apparently of a hill), to the lower buildings of a village, and finally, to the kennels and nests of the animals.
Dickinson's imagery is vivid. The mountain's hemlocks look like they are burning in flames from the sunset, while the "dun brakes" (places of dull brown undergrowth) look like they are covered in dark cinders, a witchy scene we can picture. The church steeples look red ("scarlet"), as if on fire, while the grass is colored sapphire blue. Finally, the dusk, no longer flaming like fire, "crawls" to the village, spreading a darkness that "blot[s]" out the houses and brings night to the kennel and nest.
Dickinson minutely pictures the effects of sunset on the earth. It starts out lighting most of what is in front of it as it if is on fire, then gradually imposes more and more darkness as the sun sinks away.