COL

182

COL

the lower end of the shaft, by a quantity equal to the value of

J Cl (—— + a b — c sAin which b c is the height of thev Va B • '

shaft, A B the quantity of diminution, and c M the semi-diameter at the bottom.

By Methods VII., VIII., and IX., the contour of the shaftnever terminates when continued. The curve is concave tothe axis at the bottom, and after a certain distance, it changesinto a convexity. The curve is called the conchoid ofNicomedes, who is the reputed inventor ; the straight line,in which the moving point runs, is an assymptote ; and thepoint over which the moveable rule passes, is calledthe pole.

As the curve may either fall upon one side or the otherof the axis, it is distinguished accordingly: when it falls onthe side of the axis opposite to that in which the pole issituated, it is called the first conchoid; and when thedescribing point is made to move on the same side of theaxis with the pole, the curve so formed is called the secondi j conchoid.

\ '■ This last method of describing a column by continued. j motion, has been much praised in architectural works; butj ! though the method be simple, the instrument is very cum-i I bersome. It may be observed, that as all curves are nearly

\ \ the same at tiie vertex, so small a portion as is required for

| i a column, will be the same in practice, by any of the fore-I | going forms. The most useful method, therefore, of describ-' ing the contour of the shaft, is that of Figure 6 ; the instru-' ment is much more simple, and takes less room, which, in; many cases, would not admit of that for describing the con-I ; ehoid ; and even that of forming the curve by one motion, as

I i shown at the end of Method VI., is much more convenient,

| as length or extension in one direction only, is required.

; ! But where space is wanting, Methods III. and IV. arerecommended.

: Columns are variously named, according to their mate-

j terials, construction, formation, decoration, disposition, andI i destination.

, : 1. Columns, according to their materials, are, moulded,

\ fusible, transparent, scagliola, masonic, or wooden.

! When a column is made by cementing gravel and flints of! different colours, it is called a moulded column.

‘ The art of moulding columns was known to the ancients,

j as would appear by some lately discovered near Algiers , inthe ruins of the ancient city of Csesarea; where the sameinscriptions in antique characters, and even the same defects,are to be found repeated on every shaft, which is certainly aproof of their being moulded: the cement employed in theemplastation ol columns, grows perfectly hard, and receivesa polish like marble.

Columns of fusible matter, as metals, glass, &c., are calledfusible columns ; the secret of making them is said to havebeen known to the ancients, who are also said to have fusedand cast columns of stone. Columns of this description mayalso be called moulded columns.

! When the material of which a column is made is transpa-rent, the column is called a transparent column. Thecolumns of the theatre of Scaurus, mentioned by Pliny , wereof crystal, and those in the church of St. Mark, at Venice, areof transparent alabaster.

When columns are constructed with a kind of plaster, soas to imitate marble in polish and colour, they are calledscagliola columns.

I Columns built of rough stone, or compass bricks, and| cased with stucco, are called masonic columns, or columns of

is constructed of '"^g„ e d

c g tone,

masonry; as are likewise those made in courses oi , 0l .jointed, and cemented in the best manner, with a rubsmoothed surface. See Stone Column.

When the shaft of a columnstaves, glued together, and the interior angles strengwith blockings, the column is said to be a joinery c0 ‘

See the articles Base, Capital, and Wooden Coi.uM 1 ^

2. Columns, according to their construction, are c , aJl( p-uin bands or tambours, columns in trencheons, o rcolumns. » gto ne

When the shafts of columns are formed of courses #r eof a less height than the diameter of the column, tcalled columns in bands or tambours. This methodpractised in large columns. ret> ter

3 sahito con '

- , f

When shafts of columns are formed in courses oi c .

height than the diameter of the column, they aresist of trencheons; this is practised in small columns;

the fewer the pieces, the more beautiful will the c0 ^ Ll '

1)6’

but the difficulty of raising them from the quarryand the carriage more expensive.

is g rear nam, e:

. . lu jnite“

When the shafts of columns consist of plain or orn: ," a 'ft J th 0cinctures, projecting beyond the general line of the scolumn is said to be banded, and is therefore called ^ i g ceucolumn. Columns of this description were first in t th 0

an 1

by De Lorme, in the chapel de Villers-Coherets.Tuileries, who by this means supposed the jointsconcealed.

3. Columns, according to their formation, are att&tconoidal, cylindrical, cylindroidal, or polygonal.

wou-

ld

1)6

C0»‘

,icd>

The attic column is an insulated pilaster, having £° polityfaces, of the highest proportion. Though this is foe s °inserted among the number of columns, it should n , j tj jUdeemed, but rather what we have already denomiua ^insulated pilaster. To prevent confusion, the use o 0

column, in architecture, should be restrained tocircular horizontal sections. gha^ e

A conical column has the superior diameter ot i pis' 11

than the inferior, with its sides straight in e

° f tl> 0

__ the superior ( } >ain ^ e co^ e j

shaft less than the inferior, but its exterior sidesin any plane passing through the axis. PJ uS ? 0 b sCl, j ,-nmaking the shaft swell is ancient, being mention®by Vitruvius , and has been generally followed ^

extreme diau> e ^ e

eq

lib 1

passing through the axis.

A conoidal column also has

the

# r®

section^ ot |,er

architects.

Cylindrical colmmns haveshafts of equal circles.

Cylindroidal columns are those whose ar0 ic- ,,,similar and equal ellipses, alike situated. Thesewise called elliptic columns. Instances of thisto be met with in the remains of antiquity; u tey w

of modern date, are to be seen at Koine . . ng of

Polygonal columns have the horizontal sect' j

shafts similar to polygons, alike situated. The Islu^r 0of the shafts of the columns of the portico on * ^

Delos and of the temple of Cora, are of ft 2 ,

likewise the columns of several Egyptian buildin^^. g h4. Columns, according to the decorations o ,are bark-formed, cabled, carolytic, fluted, or a tr® e ’

A bark-formed column represents the t ^ lin ^ irl ] n ated a

of the <

vi‘"

n<l s '

This is otherwise denoffli

the bark and knots.toral column.

Cabled or rudented columns have the fluting 3filled with astragals, to about one-third of t ' ie l r cor ate^Carolytic columns have foliated shafts, ^ eta , o rleaves and branches winding spirally around ^ .

posed in form of crowns and festoons. They '

i