We have already referred to the seven subdivisions of this astral world.

Numbering these from the highest and least material downwards, we find that they fall naturally into three classes--divisions one, two and three forming one such class, and four, five and six another; while the seventh and lowest of all stands alone.

As I have said, although they all interpenetrate, their substance has a general tendency to arrange itself according to its specific gravity, so that most of the matter belonging to the higher subdivisions is found at a greater elevation above the surface of the earth than the bulk of the matter of the lower portions.
Hence, although any person inhabiting the astral world can move into any part of it, his natural tendency is to float at the level which corresponds with the specific gravity of the heaviest matter in his astral body.

The man who has not permitted the rearrangement of the matter of his astral body after death is entirely free of the whole astral world; but the majority, who do permit it, are not equally free--not because there is anything to prevent them from rising to the highest level or sinking to the lowest, but because they are able to sense clearly only a certain part of that world.
I have described something of the fate of a man who is on the lowest level, shut in by a strong shell of coarse matter.

Because of the extreme comparative density of that matter he is conscious of less outside of his own subdivision than a man at any other level.