Arcana Coelestia #860
860. From these considerations it also becomes clear that all regeneration advances from evening to morning, as is mentioned six times in Genesis 1 where the regeneration of man is the subject. Here the evening is described in verses 2-3, the morning in verses 4-5. The present verse describes the first ray of light or the morning of this state as 'the tops of the mountains appearing'.
Midst
The "midst" of something in the Bible represents the thing that is most central and most important to the spiritual state being described, the motivation that drives everything else. In general this will be something we love or feel, because at the core of things we are what we love; our loves define us.
(References: Apocalypse Revealed 44, 90, 268; Arcana Coelestia 2252, 2940, 10153, 10365, 10557, 10635, 10641)