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Doric triglyph and frieze, with the usual accessories. A B gives the boundary of shadow on the femora of the triglyph, AC the boundary of shadow on the light sides of the glyphs, and AD of the shadow of the corona on the frieze. 2473. Fig. 849. is a skeleton representation Fig. 849. of a three-quarter column, forming part of an arcade. The abacus is the mere block of material Ak. In the plan ab shows the length of the line of shadow AB, and is determined by the vertical b B. In the same way, CD is found by cd and the vertical dB. k G is E- the representation of kg on the plan, and by a T vertical from g the line GH is also determined; H giving also by the horizontal line FH, in which H is already found, the situation of shadow of the point E of the abacus, as also by a vertical from f. LM N are places of the shadow of the column on the impost moulding of the arch, whereof two correspondent points are seen in l and n. 2474. The form of shadow of the console in fig. 850. will be seen on inspection to have been found from the lines aa, cc, dd, &c. on the elevation, corresponding with aa, cc, dd, &c. on the section, all which are parallel to the direction of the light, and sufficiently explain themselves. 2475. Fig. 851. is the elevation and section of a hemispherical niche, wherein are shown the shadows cast thereon by the vertical wall in which Fig. 850. it is placed. Through the centre O draw DD at right angles to the direction of the light, and from O draw OA parallel to the direction of the light: A will be found the point in the wall casting the longest shadow. Produce AO indefi. nitely; and from a, the corresponding point in the section to A on the elevation, draw aa', which will cut the surface of the niche in a'. Draw the horizontal line a'a", cutting AO produced in a”, and a” will represent in the shadow the point A in the circumference. Take any other point B in the edge of the niche, and by means of a line drawn therefrom horizontally we have the correspondent point of B in the section. From B draw in the direction of the light the line Bb"b", cutting DD on the diameter in b”; transfer the point b” in the elevation to b in the section, and draw bb' in the direction of the light indefinitely. Then with Bb" as a radius from b as a centre, describe an arc cutting bb' in b’; and from b' draw the horizontal line b'b", cutting Bb” produced in b", and b” will be the point in the shadow corresponding to B in the elevation. To avoid the confusion which

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would follow the description of the remainder of the operation, we have not encum-
bered the diagram with more letters of reference; the lines showing, on inspection,
similar applications of the process for all parts of the curve. The fact is, that the whole
of the shadow may be completed by taking the line DD as the transverse axis of an
ellipsis, and finding the semi-conjugate axis Oa by the means above described, for Da"Dis
a semi-ellipsis in form, inasmuch as it is the projection of a section of a hemisphere. This
example is applicable to the shadow of a cylindrical niche with a hemispherical head. The
line NN shows the shadow of the portion of the head, and the remainder is obtained by
the mere intersection of lines in the direction of the light from different points to the left
of N, of which enough has been already given in the previous examples to make the appli-
cation intelligible.
2476. Fig. 852, is the representation of a pediment wherein the section A is that of the

mouldings of the pediment at its
apex. In the section, ab drawn
from the projection a of the corona
in the direction of the light, de-
termines the point b therein, where-
from the horizontal line intercepted
by the line ab in the elevation, also
drawn parallel to the direction of
the light, gives the point b in the
elevation. A line from b, parallel
to the inclined sides of the pedi-
ment on the left, will give the shadow
of the corona on the tympanum on
that side, and similarly the line of
shadow from b on the right side, cd
determines the line of shadow on the
frieze, and B is the section of the
shadow of the assemblage of mould-
ings on the right.
2477. In fig. 853. is given the
plan, elevation, and section of a
square recess, covered with a cylin-
drical head. The lines AA, BB,
CC of the elevation are determined
by aa, bb, and cc of the plan; and in
the section c'c' is the representation of
the line ce of the plan. D, the point
at which the direction of the light
begins to touch the circular head,
is d' in the section.
2478. Fig. 854, is the elevation of
an arch, below which is its plan and the
shadow cast by it on the plane upon
which it stands. AA is shown by
aa on the plan, the corresponding
points in the rear of the arch, being
a' a', and a” a” the points in the
shadow. In a similar way, by BB
corresponding with bb’ on the plan
the points bob" are obtained in the
shadow.
2479. Fig. 855. is the plan and
elevation of the upper part of a house,

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wherein the upper story is occupied by an attic in the centre, against which, on each flank, the sloping roof is terminated. aa on the plan in the direction of the light, produced to intersect the hip at b, gives, by a vertical to B on the elevation, the direction BB of the shadow thereon; and BB cut by AA in the direction of the light, the length BA of the line of shadow, which may, by letting fall the vertical Aa, determine the length aa on the plan. The line of shadow ac is determined by letting fall a vertical from C, where the line of shadow is intercepted by the hip of the roof; and from c the shadow will be found on trial to return as shown in the diagram. E o Fig. 865. and D on the elevation are found, as seen in previous examples, in ee, and d on the plan, and their shadows at e'e' and d'. 2480. What is called an attic base is given in plan and elevation by fig. 856. The method of obtaining the shadows thereof in plan and elevation is now to be explained. It is an example which constantly occurs in architectural subjects, and should be well studied and understood. The operations requisite for obtaining a representation of the lines of shadow of the different mouldings in this example depend upon the principles developed in the preceding subsections. The lower portion of the figure exhibits the plan, and the middle portion the elevation of the attic base in question. The uppermost portion of it presents three sections of the mouldings of the base in question cut in three different places parallel to the direction of the light. This last portion of the figure is not absolutely necessary, inasmuch as the profiles in question might have been obtained upon the elevation; but we have preferred keeping it separate to prevent a confusion of subsidiary lines. There is moreover another advantage in thus separating the parts from each other, namely, that of immediately and more distinctly seeing the lines at each selected place, in which the rays of light separate the parts actually in light from those in shadow; and where the student is likely to meet with **. matters of perplexity, nothing should be left untried to save his time, and, what is often

more important, his patience. The mode to be adopted is as follows:–

Make on the plan any number of sections a'a'a'a', both in the direction of the light, and draw on the elevation the corresponding sections adaa, bbbb, LL being the direction of the light, draw parallel thereto tangents to the curves of the convex mouldings, and the boundaries of their shades will be obtained, as will also those of their shadows, by continuing them from such boundaries till they cut the other parts in each section, as will be more especially seen at ce. It will be recollected that in our first mention of the projected representation of the line of light and shadow we found that it was an angle of 54° 44' of the diagonal of a cube. This angle is set out in ryz on the plan. We have therefore another mode of finding the boundaries of shade and shadow on the moulding, by developing the sections a'a'a'a', bobb'b', &c., as at A, B, and C, and drawing tangents y2 to the convex mouldings for boundaries of shade thereon, and continuing them, or otherwise, for the other parts, as shown in the diagram.

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2481. In fig. 857., which represents tothe capital of a column, a similar method is used to that last mentioned for obtaining the shades and shadows, by means of a'a'a'a' and b'b'b'b', which are shown on the elevation by aaaa and . bbbb. We apprehend this will be understood by little more than inspection of it.

It is obvious that the means here adopted for obtaining the lines of shadow are precisely similar to those used in the preceding example. In this, however, the sections of the capital parallel to the direction of the light are made on the elevation, and it will be seen that many of them are not required to obtain an accurate boundary of the lines of shadow sought; for after having obtained those points from which the longest shadow falls, and on the other side - those where the line of shadow com- Fig. 857. mences, a curve line of an elliptical nature connects the points found. If the drawing to be made be on a large scale, it may then be worth the architect's while to increase the number of points wherefrom the shadow is to be projected, so as to produce the greatest possible accuracy in the representation.

2482. The shadows of an Ionic capital are given in jig. 858. The shadow of the volute on the column is obtained by any number of lines AA, BB, CC, &c. from its different

w

Fig. 858.

parts and verticals from their corresponding ones aq, bb, cc, &c. on the plan, and similarly the shadow of the capital on the wall. In this example, as in those immediately preceding, the employment of sectional lines parallel to the direction of the light is again manifest. The use of them is most especially seen in the example of the Corinthian capital which follows. As a general rule, it may be hinted to the student of sciography, that in the difficulties that may occur, they will be most expeditiously and clearly resolved by the use of the sectional lines, whereon we have thought it proper so much to dilate. 2483. The Corinthian capital in fig. 859. will require little more than inspection to understand the construction of its sciography; and all that we think necessary to particularise are the developed projections A, B, C, D, E, F of the abacus and the leaves, whereon the termination of the shadows at angles of 54° 44', as explained in fig. 856., give their respective depths on the elevation. . There is another method of arriving at the result here exhibited, by drawing sectional lines parallel to the direction of the light through the different parts and leaves of the

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capital on its elevation, as in fig. 857., and such was the mode we were formerly in the habit of adopting. It however induces such a confusion of lines, that we have long since abandoned it, and have no hesitation in recommending the process here given as the best and most likely to avoid confusion. It is of course unnecessary, in making drawings, to project more than the shadow of one capital, as in a portico, or elsewhere, similar capitals, similarly exposed to the light, will project similar shadows, so that the projection on one serves for the projection on all of them.

2484. For instruction upon the mode in which reflected light acts upon objects in shade and shadow, we must refer the learner to the contemplation of similar objects in relief. The varieties of reflexes are almost infinite; and though general rules might be laid down, they would necessarily be so complicated, that they would rather puzzle than instruct, and under this head we recommend the study of nature, which will be found the best instructress the student can procure.

SECT. IV.

working DRAWings.

2485. Working drawings are those made of the parts at large for executing the works, which could not be well done from drawings on a small scale, wherein the small parts would not be either sufficiently defined, or could not be figured so as to enable the workman to set out his work with accuracy. They are generally in outline, except the sectional parts, which are frequently hatched or shaded to bring the profiles more readily before the eye.

2486. It is obvious that though drawings made to a twelfth or a twenty-fourth part of their real size may well enough supply the wants of the workman where there is no complication in the distribution and arrangement, and in cases, where there is a simple treatment of regular forms, of right angles and the like; yet in all cases wherein we have to deal with the minor details of architecture, and in construction, where the variety of forms used is infinite from the variety of the circumstances, nothing short of drawings of the full or at the least of half the size will safely guide the workman.

2487. The art of making working drawings, which must have been well understood at all periods of the practice of architecture, involves a thorough knowledge of projection, or descriptive geometry, and consists in expressing by lines all that occurs for the developement of every part of the details of a building, in plan, elevation, and profile, each part

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