f the mass they
have to bear, as represented by the shaded circles at _a_, _a2_, _a3_,
the masses A and C are both of them very ill supported, and even B
insufficiently; but apply the four and the two shafts as at _b_, _b2_,
_b3_, and they are supported satisfactorily. Let the weight on each of
the masses be doubled, and the shafts doubled in area, then we shall
have such arrangements as those at _c_, _c2_, _c3_; and if again the
shafts and weight be doubled, we shall have _d_, _d2_, _d3_.

Sec. XIV. Now it will at once be observed that the arrangement of the
shafts in the series of B and C is always exactly the same in their
relations to each other; only the group of B is set evenly, and the
group of C is set obliquely,--the one carrying a square, the other a
cross.

[Illustration: Fig. XV.]

You have in these two series the primal representations of shaft
arrangement in the Southern and Northern schools; while the group _b_,
of which _b2_ is the double, set evenly, and _c2_ the double, set
obliquely, is common to both. The reader will be surprised to find how
all the complex and varied forms of shaft arrangement will range
themselves into one or other of these groups; and still more surprised
to find the oblique or cross set system on the one hand, and the square
set system on the other, severally distinctive of Southern and Northern
work. The dome of St. Mark's, and the crossing of the nave and transepts
of Beauvais, are both carried by square piers; but the piers of St.
Mark's are set square to the walls of the church, and those of Beauvais
obliquely to them: and this difference is even a more essential one than
that between the smooth surface of the one and the reedy complication of
the other. The two squares here in the margin (Fig. XV.) are exactly of
the same size, but their expression is altogether different, and in that
difference lies one of the most subtle distinctions between the Gothic
and Greek spirit,--from the shaft, which bears the building, to the
smallest decoration. The Greek square is by preference set evenly, the
Gothic square obliquely; and that so constantly, that wherever we find
the level or even square occurring as a prevailing form, either in plan
or decoration, in early northern work, there we may at least suspect the
presence of a southern or Greek influence; and, on the other hand,
wherever the oblique square is prominent in the south, we may
confidently look for farther evidence of th