Page:Cyclopaedia, Chambers - Volume 2.djvu/403

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yet the Sides that fall between the Ground- line and Top, fall

Stenographic PerfpeBive ; or the ProjeBion of Bodies lb very near one another, that 'twould be very difficult to ex-

on a Plane. V K & Particulars in them ; fo that the Centre mult be well

chofen in reference to this. On the given 'Point C, (Fig. n.) to raife a Perfpedlive Al- Thofe Buildings therefore, you would fee mod of, muft titude, anjwerable to the given objeBive Altitude 'P Q On be plac'd as far oft' as you think convenient from the direct the fundamental Line, raife a Perpendicular  B; and meeting the right Dine gjt, in K. In if, Mind; but this muft be done after you have drawn your Dia- ereft a Perpendicular to K C, viz. IK ; this /ifis the gonal, which is the next Thing.

5. Having pitch'd on your Centre, and having from it drawn Lines to every Divilion of the Front-line, you are to de- termine your Diagonal, A R, thus : Having with a pair of Cora- pafles meafur'd the Length of the Front-line, take your Com-

fcenographic Altitude requir'd.

Perfpeffive of a Solid

l"o exhibit the Seriography of any Solid. Find the Projec- paffes, ar >d putting oneFoot in the Centre, fee where the tionof its Bafe in the Ichnographic 'Prefpe Bive ; and in the, ner w ;u reach in the Horizon: (on both Sides if you feveral Points thereof erect the 'PrefpeBive Altitude : Thus pl ea f e ) where it refts, from that Point draw a thwart Line will the Scenography of the Solid be finilh'd, except for what lrom it to the laft Divilion of the Front; and this will betruely relatestotheShadow;whichmuftbefuperaddedfromtheLaws drawn, or pretty nigh to the Truth. That this is fo, you of Shadows, deliver'd under the Article Shadow. For an Ex- ma y cor] fider how it falls in refpefl of the two laft Centre- ample, lines : For if where the next Line from the laft is interfecled

'/b exhibit the fcenographicPerfvective of a Cube view'd An- by the Diagonal, you draw a Parallel to the Fiont between

gle-wife: Sincethe Bafe of a Cube view'd Angle-wife, and tn em, as at A to. you will have a Rhombus ; if then alithe

ftanding on a geometrical Plane is a Square view'd Angle-wife; sides be pretty equal, you may be fure you are nigh the

draw a Square on the perfpeBive Plane, after the manner laid r jgh t. Dut ;f the Sides that run toward the Centre be too

down above, raife the Side of the Square H I (Fig. 12.) per- i on g ) then Things will not fore-ftiorten enough ; if the Sides

pendicularly in fome Point of the fundamental Line JJE' 7 be not long enough, then they will fore-ftiorten too much,

and to any Point V, of the horizontal Line BR, draw right ,;. After the Front-line is thus divided, the Centre fixt, and

Lines V /and V if. From the Angles d, b^andc; draw t he Diagonal placed, take the, Breadih of the Chappel

1, dz parallel to the fundamental Line 2)JE. From the Points 1 and 2 raife L 1 and M 2 Perpendicular to the fame. Laftly, Since H 1 is the Altitude to be rais'd in a, L 1 in c and h and M 2 in d ; in a raife /a, Perpendicular to a E ', and in b and c, raife bg and c e Perpendicular to b ci ; and laftly raife d h Perpendicular to d 2 ; and let af be equal to HI, bg and e eta Li and h d to Mi ; If then the Points g, K e, /be connected by right Lines, the Scenography will be finifti'd.

This Method is general ; but its Application is not equal- ly obvious in every Cafe ; fee it further iiluft rated under the Article Scenography.

Perspective of Building, &c.

In the Praflice of the 'PerfpeBive of Building, &c. Great regard is had to the Height of the horizontal Line; all a- bove the horizontal, being feen in the upper Part, and all above it in the under Part, whence 'PerfpeBive becomes di- vided into the high and low Sight ; both which will be well illuftrated by what follows.

1o reprefeift a Building (v. g. Palace, College,^ &c.) »

A. S. which in the Ichnography is ft.ewn to be twenty Parts; becaufe this Line is Perpendicular, it muft run toward the Centre, therefore reckon twenty in the Dia- gonal, and the Rule laid parallel to the Front in that Point, will give you a Point in the Centre-line which will give the Breadth of the Chappel ; Confequently a Line drawn from A. to S. puts it into the Ichnographick 'Perspec- tive. The Length of the Chappel bring feventy Divifions in the Front-line ; reckon feventy from B. parallel to the Front-line, and there you will have a Point at C, —

The Depth of the Building from the Chappel North- ward, being 115 from the Chappel, I reckon from © 5 (where it cuts the Diagonal at tenj onwards in the Dia- gonal; and at 115. in the Diagonal, with my Rule as before parallel in this Place in the Front, I have the Point Z. in the Central-line. Its Breadth being thirty, I reckon three Divi- fions, and there is the juft Breadth there ; and fo on in every particular Part.

Having placed the Ichnography into 'PerfpeBive, you may then give every Thing its proper Height thus :

7. The Height of the Chappel being 30, I reckon 30 on .. the Front-line, and with this Length by a Square clapt to •PerfpeBive. 1. Take the Ichnography, or Ground-plat of the Front .ii ne) I drop a Perpendicular to that Height, the Building ; its Lengths, Breadths, and Depths ; by aflual and f where the ottier side G f ,h c Chappel is plac'd, having meafuring. See Ichnography ; and take its Altitude with rec i on 'd the Height upon a fuppofed Parallel, there I draw

a Quadrant. See Altitude and Quadrant.

2. Makea Scale divided into two or three hundred equal Parts, either aftually, or fo as that each divilion fignifie ten Parts : By this Scale lay down the Ground-plot, as in Figure 1 3

another Line in that Height ; then joining thefe feveral Heights by feveral Lines, you have the Profiles of each Building. Now to diverfifie thefe feveral Lines, that they confound you not, make the Ichnography, when you lay it into 'Per-

This done, having a long Rule, and a Square, which by flid- 3L fl/ -„ e ' j n difcontinued crooked' Lines, the Heights in prick't

ing on the Rule helps you to draw your Perpendiculars eaftlier, -jr.^ and t he Tops of each Building in continued Lines, as

reduce it into TerJpeBive, in its Scenographuk Appearance. ^ c ' entre. lincs art> in ,h e Table. You will likewife find

Then having drawn a Line towards the Bottom of the Pa- ^ Centre> tn0 - ' t i s not here expreft, as likewife the Point of

per for the Front or Bafe Lineas; PL Fig. 14. divide it into as Diftance by cont inuing the Diagonal up to the fuppofed

many equal Parts as you find the Building has in the Ichno- H izon whete it an d ,he Eye is placed.

graphy, or more if you pleafe : This will ferve for a S cale to determine the feveral Heights, gjte. and to thefe Divifions, with a black Lead Pencil draw Lines from the Centre, when you have chofen it ; which Choice requires Judgement on two accounts.

Having done thus, your Art mutt be employ'd for the parti- cular Expreffions of Things, by drawing and fhadowing, which is the Life of this half-form'd Figure, and which we leave to the Painter.

It remains that we fpeak of the Zow-fight: Here we fuppofe

For, if the Centre be too nigh the Front-line, then the &f) Horizontal j ufl, he Height of the Ey6i

Depth of the whole Building will fore-fhorten too much; if too far off, it will not fore-fhorten enough. This may be illuf- trated thus ; fet an open Tankard, or the like on a Stand, fo as that it be a little lower than your Eye ; if you be a great Diftance from it, you can fee very little or nothing into it ; if you come nigher to it by degrees, you will perceive the far-

bout 5

Foot

from the Bafis ; tho' 'tis generally plac'd higher, even to a third Part of the Height of the Building, that the Side Buildings may be exprefs'd more gracefully. The Diagonal is beft determined by dividing the laft Divilion of the Bafis- line into 5 Parts at G. Fig. 14 taking 4 of thefe, fome- times the whole 5 ,becaufe we determin'd before, that the Length

ther Edge fecm to be rais d a little higher than that next f the Front-line was the Diftance of theEye intheHorizon you, fo that you may fee a little Way into it ; if you come ^ poim rf Diftance. E ut here I take 4, and then make very nigh it, you fee too deep into >t more than can well be ^ ^ Diftan(:e in, he Horizon between the Eye and the expreft in P.flure. We /hall therefore find fome one Place, .^ rf Diftance . You may then either graduate the Plan which we muft conclude the moft convenient for the Draught, h< , ^^ Interfi; aions of the Diagonal with the Centre-

and which may be in general determin d to be as far oft the Front-line as the Front-line is long : This Rule, tho' it has juft grounds, yet we fometimes difpence with it pro re nata ; that we may exptefs Things with the better Appearance. 4. Confider how to place this Centre with fuch Advantage

Jiagon; lines, or elfe fuppofe it fo; and then raife the Building, as you will find by 'PerfpeBives enough of this Sott every where to be met with.

Perspective, is alfo ufed for a Kind of Picture or Painting, frequently feen in Gardens, and at the Ends

as that we may exprefs thofe Things moft, which we fGallerie f defign'd exprefsly to deceive the Sight by repre- chiefly defign to do ; for as to the bottom and top Lines of t he Continuation of an Alley, a Building, Landstip,

the Sides of the Building that run from us in or nigh the di- STTliv.

reft Line to the Centre, tho' you fee the upper Part very well,

or the like,

Perspective