CON

192

CON

ing of this description. He will also find much valuablepractical information in Mr. J. "W. Thompson’s work on the“ Construction of Stoves , and other Horticultural Buildings."

The conveniences which may be attached to conservatories,consist of retiring-rooms, seed-rooms, aviaries, &c. If therebe no sheds behind, the walls should not be less than threebricks thick.

CONSISTORY (from the Latin , consistorium) a largehall, at Rome , in which the college of cardinals meet to pleadjudiciary causes.

CONSOLE (from the French ) a bracket, or projectingbody, formed like a curve of contrary flexure, scrolled at theends, used for supporting a cornice, bust, or vase.

Consoles have been used for supporting an entire order ofcolumns, as in the barbarous architecture of the palaceof Diocletian , at Spalatro.

Consoles are otherwise denominated ancones, or trusses.

CONSPIRING- POWERS, in mechanics, such powers asact in directions not opposite to each other.

CONSTRUCTION (Latin, construo , to heap up into one)the erection or disposition of several separate parts in sucha manner, as to form a perfect and compact whole.

A good knowledge of the principles of construction, formsan essential item in the qualifications of an architect. Theprinciples of construction arise out of and are entirely depen-dent upon those of gravitation. “ Gravity, ” says an excellentauthority on this subject, “ is the source of all the principles,inventions, and ingenuity, called into action in the structureof architectural works. The weight or downward tendency oftheir materials, is the cause of buildings holding together,or falling, or being thrust apart. Gravity in its variousdynamic modifications, is the sole acting power which operatesin a building. All the mechanical perfections of scientificbuilding result from a clear knowledge of the operations ofgravity, and from the ability to direct their course: all themechanical defects of buildings, result from an ignorance ofthe laws of gravity, and from inattention or inability to counter-balance their effect. A judicious architect enslaves to his pur-pose the active force of gravity, and compels it to exert all itsforce in holding together more firmly his structure; an ignorantor careless architect or workman, allows that force to exertitself in wracking, straining, distorting, breaking, and destroy-ing his work.”

The methods in which gravity acts upon materials, are bycompression, by tension, and by cross-strain. The first ofI these modes of operation is the simplest and least destructive,

I [ unless exerted to too great an extent, and is that which formsthe basis of the most sound construction ; its tendency is tobring the particles of matter more closely together ; instancesof its application occur in all simple constructions, such asI upright piers, arches, &c. The second method, that of ten-i sion, has a directly opposite tendency to the last, and exertsits influence in disengaging the atoms from each other, it isof course not naturally favourable to construction, but thecontrary, nevertheless it is made a very efficient and usefulagent; its influence is never exerted but upon materials whichhave a strong counteracting tendency, and it is made avail-able to produce the first effect of gravity, or compression.

' Examples of its operation are to be met with in suspension-

I bridges, and in the tie-beams and king or queen-posts of

. trusses. The third method by which materials are affectedI by gravity, is cross-strain, which is a combination of the two} last, as it is tension effected by pressure, and its result is to

! tear or wrench the particles of matter asunder ; it is in prin-

' ciple totally inimical to construction, and must be avoided orcounteracted. Cross-strain occurs in unscientifically formedroofs, where struts rest upon a tie-beam, also when any ver-

tical weight presses upon any horizontal beam, as in theof bressummers ; it happens likewise, when heavy nntr ^horizontal beams have too great a bearing, the effect m ^ ^case is termed sagging, and is counteracted by camb erl °trussing the beam. __ _ „ aV ity,

Analogous, and arising out of these operations ol g. o j Sg)are the three great principles in construction—repose, e q ul P . j eand tie. The first of these is the simplest, and is the gjmost usually adopted in very ancient buildings ; it lS . 9 owhere the materials are merely piled up perpendicula V g{as to form piers or columns with cross-beams, architra ’ glintels, laid horizontally upon the piers or columns, • j 9)downwards merely with the gravity of these c° a j t ioOwithout any thrust or other inclination to destroy the P , oBof any part of the arrangement. “ Buildings construe , j n gthis principle, need only tenacity of material and unu* _foundations to be altogether perfect in construction ’ ce ,buildings of this kind, owing nothing to geometrical s .jjlead to an enormous consumption of materials; all the n> ..^ 0 g,of the horizontal spanning masses, of even a small bu r g,must be huge, and are thence immensely expensive to Pand to raise to their destined places ; if these spanning .g b t,be either so long or so brittle as to yield by their own 0 for by that which may be put upon them, the P rlD g s iak>simple repose becomes destroyed ; the horizontal m* 3 ® ,,

and the piers or sustaining masses are thrust outwar 1 ]edThe disadvantages attending this mode of construe ^edto the invention of others, yet at the same time they a poll*at attaining the same end, namely, simple repose tbi r jj-the materials and different members of a building. 1 jgjjci 03ciple of equipoise in construction is this, that all ten . uC tur e ’to disturb or produce motion amongst the parts of a sshould be counterbalanced by an equal and opposite ^ inand the most perfect exhibition of its powers is to j yuien*the arch. This principle of building allows of the \e^

of the smallest materials, and ensures stability W1 g el . a bl e l °possible quantity of matter; it is therefore far P re 0 ytyi^’the first method or principle. The third principle ^ g { »is of modern invention, and by it the quiescent s tb®structure is maintained, not by resisting the power c oijlast case, by external opposition or abutments, bu. ^ple 19fining the power by internal restraint. The P rl

case

embodied in the structure termed a truss.

iuuuicu m mo sti uutuic lohiicu. a tiuoo. , .q fit® ,

The most perfect specimens of constructive sci jjjtec* 9 'be found in the wonderful erections of the Gothic a^ ^ e \\c& ^“ The mideval Christian builders arrived to such tl 1 ^and intimate acquaintance with architectural dy na 0 fby the discovery of the way in which all the pa''^ n ab* e ^’ .materials were affected by gravity, they were e c g&merely subjecting them to the frangibility cause. ft)1 tiVj

pression, so to economize them, and reduce thei jiuO^! „that many members of Gothic edifices, after ®^ reg po>’^ l g jjyears’ devastation by time, are more sound than C °Z sub. „ ofmembers of our modern builders, which have n or tio*J ^fifty years, and which contain five times their P^.^i 8 ye<lmaterials. So admirable in general is the ® kl ' Jujccat he %the dynamic disposition of the material of a Go j l0so shrewdly are the forces of its gravitation redo pjec®compression, that the whole is like a wondershoring, sublimely and permanently imitated in * & gcb eConstruction, the art of describing a diagra ^

from given data. . , tb e

In geometrical constructions, the accuracy ° con sl _. A ,<t

depends upon that of the points by which the bn e id’’ 1 jw

1 « 1 £__ C _3 1 ~ el

mg the figure are found. It is, therefore, »" coVt -eficonsequence to ascertain the situation of pom ^ pilines crossing at right angles, or as nearly s