CUE

217

CON

e elh

®alc u j ’’'T an d tip of the hand. The English cubit may be2 ] at 18 inches, the Koman at 17.406, and the Hebrew

n inclies -

vam t DE 'FOUR, or Cu-de-Four, a sort of low sphericalthis ^ Ven like. This is the definition generally given ; but

Kieani,^ 1 ’ as a ' so t ^ le following, are altogether void of specifictheuj a °l ,-^- s they define nothing, we have only retainedS eti onar£ n ? f ° Un ? in all large encyclopaedias and builder’s8 ^°uld l6S ’ ort l et ' that our architectural nomenclature®Pheri c *i 0t ' Je bought deficient. What is meant by a lowW| lere '. r oof? I S it a segment less than a hemisphere?Efface ,\ the similarity between an oven and a sphericalC Ct ’ n °t the latter definite, hut the former indefinite?a >ch e e ~Four op a Niciie, denotes the arched roof of a° r igi n a circular plan. These two definitions are of French

c * r cui a ^ e ® a 7 be many forms of arched roofs or heads, on a?Pheri ea i™ an ’ however, the probability is, that it is either1,1 l he q, ° r , s Pherojdal, terms perfectly specific, unless it beCfJi^^hy or portion of the surface employed.

' V S d 6l) . N, in ancient Roman carpentry, answers to whatthe ridge-piece of a roof.

of

'vat,

an arched drain for conveying rills and brooks

tli,

Sl( le, to jj' ln ^ er canals or roads, from the higher level on one1 ' I ' ll ey ai - 6 °' Ver ^ eve ^ On the other side of the canal or road.l0 ^otva o re aEo eia ployed for discharging the rain-water out of^ ' Va ter- tl u PP er side of a canal. When such a drain. Passage has a descent, so as to make fit lower in theto he broken-backed,

or >e of the mechanical powers. Nee Wedge.

* sp ect ’ 111 Roman antiquity, that part of the theatre where' CSe nabl an °' s Sa h "’hich was so named on account of itst C ° Ut U of ?i t0 a wedge. This form became necessary ondj 3 ® 8 a nd a 10 eE iptic figure of the edifice, and of the stair-1Vl ded th e °° rs> "'h'ch were fixed in radial directions, andt 0 E trp]}Q r < p* ;s ' n ’° wedge-form compartments.

^°nt a j n a recess in a wall, fitted up with shelves,

1C ' es when not in use.

jjhptic eur y a r °of or vault, rising in a circular orOf 8 Ut >iini t ' 6 ’- *' rom a circular, elliptic, or polygonal plan, toM e Xt erior ’ ' V '^' ' ts concavity towards the plan, the interiori 8 ’ether th Sur ^ aces being such, that every horizontal section,° ne or the other, are sim lar figures. A cupolaterm 7 See the latter word for

n ls torv’ errne( i tholus, or dome.

ClT^jtud properties.

p 0r , , a general sense, signifies a check or restraint,ffo °yetl n JjR ick Steps, a timber nosing generally of oak,only to prevent the steps from wearing, but alsotig !lre mad ° Catt< ^ ° r P ut out t* le * r places. When thePieo l’ r °hle , 6 . t0 ret urn, the curb also returns, but whenO' 63 ’ t>on s : Sa,nst a wall, the ends of the curb orVon 118 Pr» at eacE en< l into the wall.pfiV, 0r UlE . n.circuharPl a ^ ° f a cirri ' 16 m two

a s a j So * ar or elliptieally ribbed dome, is termed a curbtir c ? a l ribs t 6 • horizontal rib at the top, on which the” r h'ain^ ?.’ m ’ n ate; likewise the plate of a skylight or a

iSx ° 1 ‘ a wel1 ’

1 also the horizontal piece of timber supported

b k, or C ll m, or d oo p, or e rS r, or r uF V

nosing-

continued plate, either scarfedor more thicknesses. The wall-

Therefore, b

ABC

men

Therefore, b i : f v

S.b k i, ors.c m l, ors.D p o, or p D qs.e s r, or v f uS.F V U, or V F wS.A B C X S.V F U x S.V F WS.ABC

by the upper ends of the lower rafters, for receiving the feetof the upper rafters, in a curb roof.

Curb Rafters, the upper rafters on both sides of a curb root.

Curb Roof, a roof formed of four contiguous planes, ofwhich each two have an external inclination, the ridge beingthe line of concourse of the two middle planes, and the highestof the three lines of concourse. This construction is frequentlydenominated a Mansard roof, Mansard being the name of itsinventor. It is very well adapted to a house surmounted bya parapet, so high as to cover the lower plane of the roof, asit gives a free or uninterrupted space from the level of itsbase to that of the summit of each lower plane, or to thebase of the two upper planes. In curb roofing, there is nodanger of springing the walls by lateral pressure, for thedistance between the base of the lower sides and the base ofthe upper sides, being sufficiently high for head-room, tiescan always be fixed in these two situations, which will preventall danger. Indeed, if the four sides of the roof be properlybalanced, the space may be made a complete void to the veryridge, or the upper part may be thrown into a cylindric arch.

A curb roof lias great advantages over a common roof, onaccount of the lower rafters pitching almost perpendicularlyto their bases, and forming very nearly a continuation of thewalls : whereas, in common roofs, the great inclination ofthe sides, and the quantity of head-room required, diminishesthe space for lodging, in the breadth of the building; in mostcases there will be a loss of about 15 or 16 feet at least, andconsequently, in small houses, no lodging-room whatever.

Curb roofs are generally lighted from dormer windows inthe lower side.

The following contains the theory and practice of curbroofing, which is perhaps one of the most interesting partsin the science of carpentry :

Proposition I. Figure 1. The position of several rafters,a b, b c, C d, d e, &c., being given in a vertical plane, andmovable about the angular points b, c, d, e, &c., while thepoints A and G remain stationary; it is required to findthe proportion of the forces at the angles, so that the raftersmay be kept in equilibrio.

Through the points b, c, d, &c., draw the vertical lines b i,c m, d p, &c., the direction of the forces; make B i of anyindefinite length, and complete the parallelogram b hik;make c l equal b k, and complete the parallelogram c Imn.Proceed in this manner with all the remaining parallelograms,making the two opposite forces in the direction of each rafterequal, and the diagonals b i, c rn, Dp, &e., will represent theforces required, as is evident from the construction. Then,to find the proportion of the weights upon any two angles,the sine of any angle is the same with the sine of its supple-ment ; therefore, the sine of the angle a b c is the same asthe sine of b k i, and the sine of BCD the same as the sineof c nm; likewise, the sine of the angle c m l is equal to thesine of the alternate angle men, and the sine of the angleDp o is equal to the sine of the angle p d q ; moreover, thesine of the angle i b k is equal to the sine of the angle me l,and the sine of the angle men is equal to the sine of theangle pDo, and so on: then, because the sides of the triangleare the same as the sines of their opposite angles, it will be,by trigonometry,

s.b i k, or i b h.s.m e l, or t b k.s.p d o, or m c n.

S.E s r, or p d q.

S.V U F, or E F G.s.i B h X s i b k X s.E P O.

S.EFG

s.iu/t x S.iiik s.vru X s.veio.