ons: let us pass to the
shaft of inferior materials.

Unfortunately, in practice, this step must be soon made. It is alike
difficult to obtain, transport, and raise, block shafts more than ten or
twelve feet long, except in remarkable positions, and as pieces of
singular magnificence. Large pillars are therefore always composed of
more than one block of stone. Such pillars are either jointed like
basalt columns, and composed of solid pieces of stone set one above
another; or they are filled up _towers_, built of small stones cemented
into a mass, with more or less of regularity: Keep this distinction
carefully in mind, it is of great importance; for the jointed column,
every stone composing which, however thin, is (so to speak) a complete
_slice_ of the shaft, is just as strong as the block pillar of one
stone, so long as no forces are brought into action upon it which would
have a tendency to cause horizontal dislocation. But the pillar which is
built as a filled-up tower is of course liable to fissure in any
direction, if its cement give way.

But, in either case, it is evident that all constructive reason of the
curved contour is at once destroyed. Far from being an easy or natural
procedure, the fitting of each portion of the curve to its fellow, in
the separate stones, would require painful care and considerable masonic
skill; while, in the case of the filled-up tower, the curve outwards
would be even unsafe; for its greatest strength (and that the more in
proportion to its careless building) lies in its bark, or shell of
outside stone; and this, if curved outwards, would at once burst
outwards, if heavily loaded above.

If, therefore, the curved outline be ever retained in such shafts, it
must be in obedience to aesthetic laws only.

Sec. VI. But farther. Not only the curvature, but even the tapering by
straight lines, would be somewhat difficult of execution in the pieced
column. Where, indeed, the entire shaft is composed of four or five
blocks set one upon another, the diameters may be easily determined at
the successive joints, and the stones chiselled to the same slope. But
this becomes sufficiently troublesome when the joints are numerous, so
that the pillar is like a pile of cheeses; or when it is to be built of
small and irregular stones. We should be naturally led, in the one case,
to cut all the cheeses to the same diameter; in the other to build by
the plumb-line; and in both to give up the tapering