_a._ Irregularity of division.
_b._ Introduction of column.
_c._ Extent of surface covered by symmetrical forms.
_d._ Greater inclosure of space in symmetrical forms.
_e._ Introduction of distinct style of architecture.
_f._ Greater height of Life forms.
_g._ Severe simplicity of Life forms produced by the
rectangular solids.
4. The sixth gift has no great increase of difficulty, and though new
forms are presented there is little complexity in dictation. The
building needs a somewhat more careful handling, inasmuch as the Life
forms rise to considerable height and need the most exact balance.
The child sees solids whose faces are all either squares or oblongs,
but of different sizes, viz., oblongs of three sizes, squares of two
sizes.
This is the last of the Building Gifts; the child having received
sufficient knowledge to be introduced step by step into the domain of
the abstract, the first step being the planes of the seventh gift.