24 ARCHITECTURE, 
struction: 1. The irregular work, opus encertum (pl. 7, fig. 7), constructed of 
stones of various shapes, but of about the same size, and cemented with 
mortar. 2. The flat square work, opus guadratum (fig. 8) of the Greeks, 
where the surfaces of all the stones are of equal size, and rectangular. 3. The 
facetted square work, as in the forum of Augustus (fig. 9), and in the tabu- 
larium (jig. 10), where the faces of the square blocks project, the edges being 
bevelled off; the jointsare thussunk in. 4. The net-work, opus reticulatum 
(jig. 6), where only the corner blocks are set horizontally, all the others 
being laid diagonally. 5. Brick-work in even -courses, opus zsodomum 
(fig. 11), where all the courses are of the same thickness. 6. Brick-work in 
uneven courses, opus pseudisodomum (fig. 12), where thick and thin 
courses alternate. 
In constructing very thick walls, the two outer faces only were laid sym- 
metrically, the space between being filled up with mortar and small stones ; 
such walls were called filled walls, emplecton, and of these there were three 
different kinds: 1. Where the two faces (fig. 18 aa) are built without any 
connexion, and the space, B, between them is filled up. 2. Where the 
bricks in the faces are laid alternately as headers and stretchers (jig. 14, 
upper part), the latter thus affording a firmer connexion of the two faces, by 
projecting into the rubbish between them (jig. 14, lower part). 3. Where 
some of the bricks are stretched through both faces of the wall. Walls of 
this description are even constructed nowadays, but they ought always to 
be considered as very inferior work. 
Tue Cotumy. After the walls were built of stone, the wooden posts of 
course soon gave way to stone pillars. These were at first short, and there- 
fore in a single piece; but it soon became necessary to have them longer 
than single stones could conveniently be procured, in consequence of the 
increased height of the buildings, and they were then constructed of several 
disks (tambours) placed one onthe other. The quadrangular pillar, however, 
in no long time must have become offensive to the eye accustomed to the 
circular forms of trees, and the stones were rounded to form the column. 
After a time, the upper part of the column, or more properly the block 
which was placed on the top to afford a better bearing for the beams, was 
moulded into an oval or convex shape, the echinus (pl. 19, fig. 1). To form 
a more tasteful connexion betweeen the column and the echinus, a few hori- 
zontal stripes were made in the lower part of the top piece (pl. 20, jig. 9, 
left lower diagram), and another stripe was afterwards cut in some inches 
below, and so the neck of the column was formed. The mouldings of the 
stripes and of the echinus itself are sometimes a little different, as shown in 
the several Doric capitals (pl. 19, figs. 1, 2, 3). To give the column greater 
strength and stability, it was made wider at the foot than at the neck and 
capital, and to make it appear lighter it was channelled with perpendicular 
stripes, and hence the origin of the flutes. These flutes were sometimes put 
close to each other (pl. 19, fig. 1), or a small ridge was left between them 
(fig. 7). Sometimes the shaft was left plain (jigs. 4), and at a later period 
the column itself was decorated with foliated work (jig. 25, 26). Some of 
the Doric columns have flutes of a few inches in length close below the 
24 
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