In speaking of the softening of outline and flattening of bulk due to atmosphere we have frequently alluded to the effect of distance on the appearance of objects. The further off the latter are, the more atmosphere will intervene, the less distinct will they appear. In the case of distant hills, the ups and downs of the ground, the bulk of the trees, even the stability and massiveness of “the everlasting hills,” may be softened and flattened into what seems to be only a faint mass of color.