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424

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We have gone at length into this subject, on account of itsimportance ; which has caused it to be most earnestly dis-cussed. In 1855, the Metropolitan Commission of Sewerswas superseded by the Metropolitan Board of Works, theformer having failed, it was thought, in carrying out thepurposes for which it was appointed. The sewage and drain-age of the metropolitan district is the more especial objectof the new body. In 1856 and 1857, its engineer, Mr. Bazal-gette, assisted by Mr. Bidder and others, made reports on thesubject, which Captain D. Gatton (a government engineer),Mr. F. O. Ward, and others, opposed; and which Sir Ben-jamin Hall, then her Majesty’s Chief Commissioner of Works ,refused to sanction. In 1858, so great was the alarm excitedby the state of the Thames, into which the metropolitan sew-age is discharged, that immediate action was deemed necessary;and the Metropolitan Board was authorised to carry out thenecessary works without control ; and to raise £3,000,000towards the expense. After some delay the plan of Mr.Bazalgette was adopted, and two great systems of drainagefor the metropolis have been executed. The outfall for eachsystem is at a point a few miles below Woolwich, on eitherside of the river, where the breadth of the stream will besufficient to carry off both the ordinary drainage and anyextraordinary fall of rain.

SEXAGESIMAL, (from the Latin, ) the division of aline, first into 60, then each of the parts into 60, andeach of these again into 60, and so on, as long as divisioncan be made.

This division is principally employed in dividing the cir-cumference of a circle, and was much used in ancient astro-nomy. The French have adopted the centesimal division,which is far more convenient for calculation.

SEX AG ON, or Hexagon, a six-sided figure.

SHADOWING, in drawing, the art of representing thevarious degrees of light and shade by means of a dark fluid,or liquid.

The paper intended to be drawn upon, having its roughedges cut off, ought to be wetted, or uniformly moistened,and pasted round its four edges upon a board, observing, indoing this, that no part of the paper ought to be suffered todry before the edges that are pasted, as the paper will beginto shrink; and, consequently, by its motion towards the cen-tre, will loosen the edges: as soon, therefore, as the middlepart appears dry before the edges, it ought to be moistenedagain with a spunge, and the spunging should be repeated asoften as may be found necessary; and, when the paperbecomes dry, it will be perfectly flat, and fit for use.

In order to lessen this trouble, some have drawing-boardsframed so as to include a panel, which is let into a rebate,on the inner edge of the frame, and fastened, by means ofbars, upon the back of the board.

The paper being wetted on the side intended to be drawnupon, the dry side is laid upon the face of the panel, nowout of the frame, so that the edges of the paper project alikeon all sides, over the edges of the panel; then laying holdof the paper by the edges out of the panel, place it overthe aperture in the frame, with the underside reversed, andpress it in ; after which, bolt the panel to the frame by meansof the bars, and the edges of the paper being inserted in theseam, or joint, between the edges of the panel and the adja-cent edges of the frame, will prevent the paper, as it con-tracts in drying, from returning towards the centre, and,when dry, it will be flat and extended; but this method canonly be practised in small drawings. The former must,therefore, be considered as the general plan of fixing thepaper.

The fluid commonly used in architectural drawings is

be

Indian ink dissolved or mixed in water. The ^doing it is this: fill a small cup with as much W a e m 11 ^’be necessary for the quantity of ink intended t° ^ ve tte<l 10then rub the ink upon the tip of the fore-finge^ be 00 ” 1 ?.,water, and wash it off in the cup: when the wa e i,o"sufficiently dark, it will be fit for use. This met ^ faC ti 0ever, too tedious for general use, the more freque s | l0L jld 0is to rub it up as other colours. The stick of ' U j n j 0 p’ eC . 6 jrubbed quite dry, otherwise it will be apt to fm * j 3 csm 0and become unfit for use. The liquid thus maink. or colour. ; D g. ,

The next thing to be done is to outline tbe . c j e3 °by . rStraight lines are drawn with a steel pen, cir 3il bl ecompass, and curve lines by hand, with camel rU ier a1 'pencils, or with a fine-pointed pen, or with curdrawing pen. _ jbe ste g

In drawing very fine lines, the inking-poi nts ^ no 1 0pen and compasses ought to be kept very s | iar Pg n j s hedi *.much as to cut the paper. The outlines being 0 r rUpaper ought to be rubbed clean, and then S P U .?° the l > n ?'bed with a soft brush and water, in order to so^ ^ oJ . e freeand to make the paper receive the shadowing ^ ra iseIf the paper be even spunged, or brushed, so a9 ^ e for P rnap in a small degree, it will be the more favourducing clear and soft shadows. eT> it ° a ° 0 f

In laying the shadowing colour upon the p a P^ cam . . 3to be spread over the surface uniformly WI 1 . q U anb j tsable hair pencil, flowing freely; but not ’ n o S ^ v [ ie n dr^g

sm"

as to stand in hollows upon the paper, a3 > g r st

becomes cloudy. In making a uniform tirt, the• , -v. , ° j.-.i—oas to whim 1

lig

lit,

to be considered is, the degree of darkness ^ " ‘ g ve ,-y - ~ (face is intended to be made. If required to ^.^t:one tint, or the shade once gone over, will be J uC ing ,yif dark, several tints will be necessary. 1“ f be nt *,jllseveral degrees of darkness, every tint ougi

to , b ? n3

re petit 10 £ i,e

dry before the next is laid; the number ° l axtens ioO 0 -

depend upon the depth of the colour and th®

surface to be shadowed. It may be observe , ^ an y dec (0est tint, often repeated, will darken the surface ^ dedi cate ft tefrequired. But that too much time may that tl‘ e gqjj be

required. ±sut that too much time may *■ . t tb®

laying a fine tint, it must also be observed, y e ^ v erthe facility with which the tints are laid, 11 ® ^ £0required to darken the surface. This f aC1 1 Jtained by sufficient practice. is the

Wi>

be

the'

ned by sufficient practice. _„ve. is tne „ive»

SHADOWS, The Doctrine of, in persped 1 ^ ^and practice of representing shadows, as pr°J e : or os If* *><■point at a finite distance, such as a candl ^ j„fini te ', t th 0from the sun, where the distance, though no^ t' a 0 ge,

the sake of simplicity, considered as such, i t j t j s p a P ofrays may be all parallel ; or otherwise, ^ a ll p 01the rays may be supposed as proceeding * flig bt

space in parallel lines. deP r * ve ^ °

Definition 1.—A line of shade is the line jjfk

by an opaque point opposed to the luminary- ^ ue ,° xDefinition ‘2. —A plane of shade is aI ^ y roI11 tb® jplane, occasioned by the privation of hg - na ry; 0,1position of a straight line opposed to the imj g thr® °it is evident, that every plane of shade wi

luminary. n f bodied ° CC ..

To find the shadows, upon the surfaces J lit

by the privation of the sun srafiProposition I. — Given the vanishing , - n g p° l11 0 iflt j .vanishing point of the sun's rays, the van f ,; oJl of t ii>seat of a ray on the plane, the represen p° l! e $0*

space, and the representation of the sea ■ . ^ g t e f e Pplane ichose vanishing line is given; °d -^e.tion of the shadow upon the plane of the p

oh'or 1