CIVIL ARCHITECTURE. 



599 



Fractice. 



rtxxxii. 



Fig. 2. 

 No. Land 

 f. 



Cavcttn. 

 1.4. 



C ma-recta 

 fig. S. 



rima-rc- 

 veria. 



Fig. C. 



Apopliyjc, 

 Fig. 7. 



Fig 8. 



Fig. 9. 



OreeV ovo- 

 !o. 



It 11. 



given Fig. 2. First, let the height and the projection 

 be eq'ial to each other. Draw a b equal to the height, 

 and be at a right angle with, and equal to, a b, for the 

 projection ; then with the radius b a or be describe the 

 arc a c, which is the contour of the ovolo. But if the 

 projection is not equal to the height, but less, as in Fig. 

 2. draw a It and be forming a right angle as before, nb 

 being made equal to the height, and b c equal to the pro- 

 jection ; from the point of reces a, with the height a b, 

 describe an arc b d ; and from the point c of projection, 

 with the same radius, describe another arc cutting the 

 former at rf; lastly, from d, with the radius d* or dc, 

 describe the arc ac, which is the contour required. 



The methods of describing the cavetto, Fig. 3. and 4. 

 are the same as that for describing the ovolo, the one 

 being the same as the other reversed. 



To describe the cima-recta, Fig. 5. Join the point 

 of recess a to the point of projection 6 by the line a b ; 

 bisect a b in c, with the distance b c from the points c, b ; 

 describe the intersection e, and from the points a c, with 

 the same distance, describe the intersection d ; from d, 

 with the distance da or dc, describe the arc ac; and 

 from e, with the distance cb or re, describe the arc be; 

 and acb will be the contour of the cima-rccta required. 

 If the curve is required to be made quicker, we have only 

 to use a less radius than that of a c or c b, in order to de- 

 scribe the two portions of its contour. 



The same description applies to the tima-reversa, Fig. 

 G. by the same letters of reference. 



To describe the apophyge, Fig. 7. the projection be- 

 ing piven. Let a b be the projection, and ace a line 

 which it is required to touch. Make a c equal a b, and 

 with the distance a c or a b from the points 6 and c de- 

 scribe the intersection d ; from the point d, with the ra- 

 dius Ab or d c, describe the arc be, which is the contour 

 of the apophyge. 



To describe the apophyge so as to touch a right line 

 given in position at the point of projection, Fig. 8. Let be 

 be the right line ; and a b the projection of the moulding ; 

 draw a c df at a right angle with a b ; make c d equal to 

 cb; draw be perpendicular to be, and de perpendicular 

 to erf ; from the point e describe the arc b d, which is the 

 contour of the moulding. 



To describe the scotia, Fig. 9. the extremities a and 6 

 of the curve being given. From the projecting point 6 

 erect b d e, and from the receding point let fall age per- 

 pendicular to be, the horizontal of the moulding; add 

 the half of ac and two-thirds of Ac into one length, 

 which set from b to d ; from the centre d, with the dis- 

 tance d b, describe the semicircle bfe ; draw the straight 

 line e of, and dgf; from the point g, with the distance 

 g a or ef, describe the arc af: then will aft be the con- 

 tour ofthe scotia required. 



To describe an ovolo, the tangent a c at the receding 

 extremity a, and its projection at b being given, Fig. 10. 

 and 1 1 . Draw the vertical line eld; draw b e parallel 

 to ca, and ae parallel to cb; produce ae \.of, making 

 ef equal \.oea; divide eb and be each into the same 

 number of equal parts ; from,/, and through the points 

 of division in a b, draw right lines ; also from a, and 

 through each of the divisions in b c, draw another sys- 

 tem of lines, and the corresponding intersections of each 

 pair of lines will be as many points in the curve as there 

 are pairs ; then a curve being drawn through the points, 

 will be the greater part of the contour. The remaining 

 part bg may be found in the same manner, by drawing 

 lines from a through the points in be instead of f, and 

 drawing lines from bd to /j instead of be to a. The curve 

 drawn in this manner i* a portion of an ellipsis, something 



greater than the quarter of the whole. The recess ofthe Practice, 

 moulding at its projecting point is denominated the quirk. SP Y* < "' ' 

 Fig. 10. is adapted for entablatures; and Fig. 11. having 

 a large projection, to capitals of Doric columns, such as 

 may be seen in the temple of Corinth, and in the Doric 

 portico at Athens. This method, though easy, gives 

 the extremity of the conjugate axis, between the rece- 

 ding extremity a, and the point of projection b ; but 

 the following method gives the extremity of the shorter 

 axis, where the tangent commences, at the receding ex- 

 tremity of the contour of the ovolo. 



To describe the ovolo, supposing the extremity of the PLATE 

 conjugate axis to be at the point of contact a, Fig. 12. CLXXXII. 

 Join a b, which bisect in e, and draw cefi make nflk Fi g- 12 - 

 perpendicular to the tangent a c, then the point _/ will be 

 the centre ofthe ellipsis: draw_/A i parallel to ac; take 

 the distance fa, and from the point b cross the line fi et 

 h ; produce bh to /, and make/j' equal to hi ; thru with 

 the semi-transverse fi, and the semi-conjugate fa, de- 

 scribe an ellipsis, and the portion of the curve contained 

 between the extremities a and g, will be the contour of 

 the moulding required. This method is recommended as 

 producing the most graceful form of an ovolo, as the 

 lower extremity of the curve begins at the point of con- 

 tact. From the large projection here given, the mould- 

 ing is adapted to Doric columns. 



To decribe the hyperbolical ovolo, as used in Doric 

 capitals, the same things being given as before, Fig. 13. Fig. 13,. 

 ILrectadefg perpendicular to the horizon, and draw 

 cd and be at right angles to adefg: make eg equal to 

 a e, and ef equal to ad ; join bf, divide bf and be in- 

 to the same number of equal parts, and draw lines from 

 g through tlic divisions of bf, also lines from a through 

 the divisions of b c : Each corresponding pair meeting as 

 before, will give the points in the curve of the hyperbo- 

 lical moulding. This is the general form of the ovolos 

 in the capitals of the Grecian Doric. 



To describe a scotia, Fig 1*. Join the extremities a Fij. 14* 

 and b of the moulding ; bisect a b in c ; draw ecd paral- 

 lel to the horizon ; make cd equal to the recess of the 

 curve, and ce equal to cd ; then with the conjugate dia- 

 meters till and ed describe the curve adb, which will be 

 the contour of the moulding required. 



Fig. 15. represents the form of the annulets as applied Annulets. 

 in Fig. 13. where the receding parts are in the tangent F| 8- 15> 

 at the bottom of the curve ofthe ovolo. 



Fig. 16. represents another kind of annulet, which fig. 16. 

 has a vertical position. This form i only to be found 

 in the Doric portico at Athene. 



Fig. 17- represents a curious Grecian moulding, to be Fig. 17. 

 found under coronas. 



To diminish the shaft of a column, Plate CLXXXIII. To diim- 

 Fig. 1. Let A B be the altitude of the column, and BC nish c - 

 the diminution at the upper end of the shaft ; divide AB '" mn - 

 into any number of equal pans, and divide the projection 

 BC into the same number ; draw the lines Ib, 'Id, 3c, &c. "' ** 

 at right angles to the altitude ; and draw other lines from 

 the points 1, 2, .3, &c. in BC towards A, to intersect 

 with the former parallel lines at the respective points b, *"> * 

 c, d ; then A. bed efC, will be the curve line of the sec- 

 tion c f the column. 



But suppose it mere required to give less swell to the 

 column, as in Fig. 2. Divide AB as before, and DC 

 into two equal parts at D ; divide DC into as many equal 

 parts as AB ; then proceed as in Fig. 1.. Or thus: sup- 

 pose EF to be the axis of the column, EG, EA the se- 

 mi-diameters at the bottom, and FN, FC the semi-dia- 

 meters at the top ; on AG, as a chord, describe the eesr- 

 3 



