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Future 2.—Another cove-bracket, of which one side hasless projection than the other, bgd the plan of the angle,as before ; the bracket A G b, the angle bsd, and the posi-tion of the line, G e, are given ; h g e, being an obtuseangle, viz., the angle of the room. The ordinates, m n, ofone side of the room, are taken from the ordinates, k i, of thegiven bracket, a b g.
SPAN-PIECE, a provincial term in Lincolnshire, andperhaps in other counties, for Collar-Beam, which see.
Span-Roof, a roof consisting of two inclined sides. Theterm is used in contradistinction to shed-roofing. Span-roofing may have simple rafters, with or without a collar-beam ; or the roof may be trussed; in which latter case, theterm applies only to the external construction.
SPECIES OF TEMPLES : these are determined by thenumber of columns in the front of the portico ; which, withtheir distance from each other, is regulated by the diameterof the columns at the bottom. See Temple.
SPECIFICATION, a detailed and formal description ofan edifice to be erected, the materials to be used therein, andthe particular uses to which they are to be applied. Speci-fications are provided for the guidance of the builder inmaking his tender for work, and are appended to the con-tract. They are usually divided into several heads, accord-ing to the different trades employed in the work, and oughtto be made out with great accuracy and precision; the moresimple they are, the better.
SPECIFIC GRAVITY, a comparison of every solid, orfluid, with the weight of the same magnitude of rain-water.Rain-water is chosen as the standard of comparison, onaccount of its being less subject to variation, in differentcircumstances of time, place, &c., than any other body,whether solid or fluid. And by a very fortunate coincidence,at least to English philosophers, it happens, that a cubic footof rain-water weighs 1,000 ounces avoirdupoise ; and con-sequently, assuming this as the specific gravity of rain-water,and comparing all other bodies with this, the same numbersthat express the specific gravity of bodies, will at the sametime denote the weight of a cubic foot of each in avoirdupoiseounces, which is a great convenience in numerical com-putations.
From the preceding definition, we readily draw the follow-ing laws of the specific gravity of bodies, viz.,
1. In bodies of equal magnitudes, the specific gravities aredirectly as the weights, or as their densities.
2. In bodies of the same specific gravities, the weightswill be as the magnitudes.
3. In bodies of equal weights, the specific gravities areinversely as the magnitudes.
4. The weights of different bodies are to each otherin the compound ratio of their magnitudes and specificgravities.
Hence it is obvious, that if in the magnitude, weight,and specific gravity of a body, any two be given, the thirdmay be found ; and we may thus find the magnitude ofbodies, which are too irregular to admit of the applicationof the common rules of mensuration ; or we may, by know-ing the specific gravity and magnitude, find the weight ofbodies which are too ponderous to be submitted to the actionof the balance or steel - yard ; or, lastly, the magnitudeand weight being given, we may ascertain their specificgravities.
Example 1.— The weight of a marble statue being 74 s ®.avoirdupoise, required the number of cubic feet, &yc., which itcontains ; the specific gravity of marble being 2742.
Since a cubic foot weighs 2742 ounces, we haveas 2742 : 748 X 16 : : 1 : 4.36 feet.
Example 2.— Required the weight of a block °f 9 , j2whose length is 63 feet, and breadth and thicknessfeet; the specific gravity of granite being 3500.
Here 63 X 12 X 12 = 9072 feet: then againas 1 : 9072 :: 3500 : 31752000 ounces : e „-
or 885 ton, 18f cwt. The above are said to be thesions of one of the stones in the walls of Balbec. ^odi® 9
Other properties relating to the specific gravity o.are as follow, viz. , _ eC ifiC
1. A body immersed in a fluid will sink, if lt9 j e gg, tb®gravity be greater than that of the fluid ; if it b e , .’andbody will rise to the top, and be only partly immeis vV ;llif the specific gravity of the solid and fluid be e 4 u . a ’j tremain at rest in any part of the fluid in which
be placed. jnuch
2. When a body is heavier than a fluid, it loses ® 0 f tb®
of its weight when immersed, as is equal to a quanti yfluid of the same bulk or magnitude. • , nn that
the body, then -°^ tke duid be greater u»— .
Part immersed, is eaST'f ° f the f,uid displaced by &•And hence, as the -ft ° £ le weight of the whole bo f** body, s’ i s ^ity of the fluid is to that
immersed. e Magnitude of the body to the p^
immersed 6 hfthe same fluid ° f 6qual solida are aS ^ ^byjbe 8ame P imme r fed solid du ' da are as the welgIlts ^
speciBcgwvitf&nfh*! 1 ? foIIowin g rules for ascertaining
To find Ihesle^ 1 S °! ids and duids.generally by a body .—This may be d
trived for th e eaq ° the hydrostatic balance, which is ®
of bodies, either iZiir ? Xa , Ct d ? ter mination of the we ’f, el3uid, from the diffhr» ’ or ' V ie . n immersed in water, orothe solid and 6nCe , of which the specific gravity of
1. kFhen tf /J aaybecom Puted. u ti
out of water and^ heavier than water.—Weigh it bo
water J then say,
As thewmghtlost in watereu • , le "^ole or absolute weight,
To tl t 8 r P ? cldc gravity of water^J** VS' - water.—Inthat tJ Je mass 6 ° ? not ^ er body heavier than >va u e r.Weigh the of the two may sink t0 $ te \y,
both out of the 1 °^ 7 a,ld tbe eompound body sep«i j,
^sintheJZ T e, ' a,,d in i[ ; and find howweight in air- su btracting its weight in water fi &
the greater subtract the Jess of these remainders
A f n , USe ti,e following proportion :
the last remainder
i a . weight of the light body in air,
T° h 1 * e s P ec ‘f' c gravity of water3. When S ^ cific 8 ravit y °f tbe body. ■ re d.''
Take a piece 9r , avit y °f *he fluid “L^Lvrty >
weigh it both ■ f S , Ule body of known speci&c g r ^we£ht bvtS- ’ n a ," d out the fluid, and find the Jo"
° 7 the difference of these two ; then say,
s the whole or absolute weight
I s ^ loss of weight,
T° 3S t specific gravity of the soli®
The fnllrv -° * 16 s P ec *fic gravity of the fluid. ^ „faef er ^°f the ta ^ e exili hits the specific gravity 0O (e
extenliZ C ° mtn0n bodies i it is extracted f^J ot h«'tables of <1 oae & lven i n Gregory’s Mechanics; , £&et'son It S, “ lkr kind will befolnd in the works of
than
by