would perhaps do a little more justice to the labors of the man who
contrives the plan, which they think such an easy business; and no doubt
it may appear an easy business, because the very characteristic of a
really good plan is that it should appear as if it were quite a natural
and almost inevitable arrangement.

Just as it is said in regard to literature that easy writing is hard
reading, so, in regard to planning, it is the complicated and rabbit
warren plans that are the easiest to make, because it is just doing what
you please; it is the apparently perfectly simple and natural plan which
springs from thought and contrivance. Then there is the next step of
raising the walls on the plan, and giving them architectural expression.
This must not be thought of as an entirely separate problem, for no
truly architectural intellect will ever arrange a plan without seeing
generally, in his mind's eye, the superstructure which he intends to
rear upon it; but the detailed treatment of this forms a separate branch
of the design. Then comes the third and very important problem--the
covering in of the space. Next to the plan, this is the most important.
All building is the covering over of a space, and the method of covering
it over must be foreseen and provided for from the outset. It largely
influences the arrangement of the plan. If there were no roofing, you
could arrange the walls and carry them up pretty much as you chose, but
the roofing of a large space is another matter. It requires extra
strength at certain points, where the weight of the roof is
concentrated, and it has to be determined whether you will employ a
method of roofing which exercises only a vertical pressure on the walls,
like the lid of a box, or one which, like an arch, or a vault, or a
dome, is abutting against the walls, and requires counterforts to resist
the outward thrust of the roof. We shall come upon this subject of the
influence of the roof on the design of the substructure more in detail