Sentence:  It was not far from the house; but the ground sank into a <WSD>depression</WSD> there, and the ridge of it behind shut out everything except just the roof of the tallest hayrick. As one sat on the sward behind the elm, with the back turned on the rick and nothing in front but the tall elms and the oaks in the other hedge, it was quite easy to fancy it the verge of the prairie with the backwoods close by. 
Meaning of the word marked with <WSD> tags:  An area that is lower in topography than its surroundings.