This verse is not easy to understand as it is written. If we paraphrase this verse, and take some liberties based on other scriptures, the meaning is more clear, "And in that day when Zion is established in great power and glory they (the inhabitants of Zion) shall roar against them (their enemies) like the roaring of the sea; and if they (their enemies) look unto their own land, behold, darkness and sorrow, and the light is darkened in the heavens thereof. But if they look unto the land of Zion, behold, great light and joy, and the saints are protected by a pillar of cloud by day and a pillar of fire by night." (See DC 45:70, Moses 7:17, 61, 2 Ne. 14:5)