1S46.J 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



325 



TRABEATE AND ARCUATE ARCHITECTURE. 



The adoption of technical terms in any art usually results from a sacrifice 

 of one or other of the two essential requisites of a perfect nomenclature — 

 perspicuity and conciseness. A new compendious term which supplies 

 the place of a long periphrasis affords to the initiated the advantage of 

 brevity — while to the uninitiated it is liable to appear pedantic and obscure. 

 So that the addition to the list of technicalities of an art already containing 

 a large number of them should not be made except where the new term 

 supplies the place of long and continually recurring phrases, and is of it- 

 self sufficiently significant to be remembered without difficulty. 



Now, in developing the principles of constructive architecture, we are 

 constantly presented with this fact — that the architecture of every age and 

 country of the world is separated as regards mechanical structure into two 

 classes — that in which the masonry sustains vertical pressures only, and 

 that iu which both vertical and lateral pressures are sustained. The 

 former consists of horizontal entablatures supported by vertical imposts, 

 unjointed blocks or architraves resting at their ends on piers, and 

 rectangular frame-work formed of transverse beams or joists sustained by 

 upright timbers. In the other great division are contained all structures 

 in which the intervals betweentwo piers, columns, or abutments, or between 

 the sides of iiu embrasure or other opening in a whII, are spanned by an 

 arch consisting of many stones so shaped and united as to be capable of 

 resisting the pressure of superincumbent weights. In the science of INle- 

 chanicsthe principles of these two methods of construction are distinguished 

 thus — in the first method — that in which spaces are spanned by one single 

 block or beam, the material is influenced by two equal and opposite forces 

 of tension and compression — in the latter method where spaces are spanned 

 by more than one block, the internal forces of the material are generally of 

 the nature of compression only, but there are moreover lateral forces ex- 

 ternal to the system, exerting outward thursts or pressures which must be 

 sustained by external appliances. 



It is immediately obvious that these different mechanical principles 

 must, where the decoration is dependent on the construction, produce alto- 

 gether different architectural forms. Where the embrasures or intercolum- 

 niation are spanned by a single block, the difliculty of procuring single 

 blocks of great length will render it necessary that the piers or columns 

 should be comparatively close together, and as the pressures are wholly 

 vertical, the only requisite for strength is that the columns be not crushed 

 by the weight on them, and no great precautions need be taken to prevent 

 them from being overturned by lateral pressures. Consequently, in the 

 one mode the columns will be of nearly uniform thickness throughout their 

 height, and the intercolumniations will be narrow: in the other mode, 

 the intercolumniation may be increased and the piers will have enlarged 

 bases. 



These considerations in their utmost generality, distinguish all architec- 

 ture into two grand classes : and when we regard the value and exceeding 

 comprehensiveness of the classification, it does not seem unreasonable to 

 demand that distinctive appellations should be appropriated to it, and be 

 received among the recognised terms of architectural nomenclature. For 

 the names of the two classes no words seem more natural than those con- 

 tained in the title of the present paper, and accordingly we assume that 

 all architecture is divided into two kinds — Traeeate and Arcuate. 



Trabeate architecture is the most ancient. Very little reflection will 

 show that a system of construction, identical with that of the primitive 

 timber hut, would be the earliest adopted, and that the arch, a structure 

 requiring much mechanical skill in the workman, and much theoretical, or 

 at least experimental, knowledge in the architect, would be one of the 

 appliances of later art. The early history of the arch is very obscure; 

 it is however certaiu that neither Pelasgic, Babylonian, Egyptian, nor 

 Grecian architecture present any trace of arcuate construction : the earliest 

 examples which have had any important influence on modern art are cer- 

 tainly to be found among the Romans. Tlie nature of this influence is 

 admirably described in the following passages from Professor Willis's 

 Architecture of the Middle Ages. 



" After the arch and the vault had enabled the Romans to construct 

 buildin2;s with small materials, it is curious to observe the struggle by 

 which the arch forced itself into the Decorative construction. At firsi, 

 the arch is used sparingly, and only in cases of necessity. It is either hid 

 under th^ plaster, or it is kept subservient and as if the architect were 

 ashamed of it as a clumsy and economical expedient, all the resources of 

 the Decorative construction are emploved to cunccal the important place it / 

 No. 110.— Vol. IX.— Notembeb, 1S4G. 



holds in the mechanical structure of the building. Gradually we find the 

 vault first, and then the arch, assuming a more prominent place only to 

 pTO<\uce that discoiJatit effect which must ercr result fr urn the attempt io 

 harmonise two cimtendiuii; principles. 



" For when the arch is employed, the diagonal strains must be provided 

 for; and as the Decorative system of the Greeks wai founded upon a 

 mechanical structure that only exerts perpendicular pressures, it is clear 

 that the diagonal ones must be concealed by huge rectangular masses, 

 decorated so as to appear as if sustaining vertical pressures only, unless 

 we choose to invent new forms for the diagonal props. The Romans at- 

 tempted concealment, and hence introduced discordance between the 

 decoration and mechanism of the structure. The Gothic builders, in later 

 times, more wisely adapted their decoration to the exact direction of the 

 forces required by the vaulted structure." — p. 17. 



Every word of this extract demands the most attentive consideration. 

 No other comment is here requisite tlian the citation of a few instances of 

 that violation of the principles of faithful architecture which the Romans 

 exhibjied in their attempts to combine arcuate with trabeate construction. 

 In the Coliseum the weight of each story is in reality sustained by tiers 

 of arches ; in addition to these, however, there are entablatures between 

 the stories which, as well the columns between the arches, are merely affixed 

 to the building for show, and have no constructive purpose. The same 

 remark applies to the Triumphal arches, one and all : and these moreover 

 involve the additional solecism of being treated not as members of a 

 building, but as integral buildings of themselves— they have all the strength 

 and solidity requisite for sustaining an immense superstructure, but like 

 the monumental columns known by the names of Pompey and Trajan, are 

 isolated and sustain nothing but their own mass, or at most that of statues 

 of which the weight is ridiculously disproportionate to the solidity of the 

 supports. This species of solecism has found great favour in our own 

 country, and is exhibited on a large scale in the Barriere de I'Etoile, at 

 Paris. 



Rluch, however, of the architecture of the Romans was free from the 

 incongruity described by Professor Willis, and even where it exists there 

 is frequently discernible in spite of it (not in consequence of it), great 

 beauty and pictorial etfect, which cannot be overlooked without an in- 

 tolerant adherence to systematic principles. It will, however, be our 

 business to show hereafter that the i\oinans gained nothing by this sacrifice 

 of purity and harmony — that equal vigour, variety, and depth of shadow 

 may be attained without violating the principles of constructive decoration 

 which were observed in Greek and Pointed architecture. 



The opinion of the authority cited above is confirmed (with a modifica- 

 tion similar to that which we have just suggested,) by Professor Whewell, 

 who, in his " Noies on German Churches," speaks of " the Roman intro- 

 duction of the arch into Grecian architecture" as (ollows :— 



"In this manner, then, were produced two planes of decoration ; one 

 consisting of the traditional scheme of the structure ; the other, behind it, 

 containing the real construction — the arch and the impost mouldings. And 

 though this combination is, in reality, incongruous and inevitably tniiisi- 

 tional, it would be impossible for a genuine artist not to perceive that it 

 disclosed an extraordinary richness and depth of effect." — p. 8. 

 Again, — 



" The introduction of the arch undermined the Grecian system of en- 

 tablature, and introduced a double plane of decoration : the ruin of art 

 and taste supervening on this, broke up still further the Roman traditional 

 arrangement; caprice and the love of novelty introduced new forms of 

 members and ornaments into this incoherent mass: arches, of various 

 shapes, were invented or borrowed ; the Byzantine dome was added to 

 the previous forms of Roman vaulting. So far, all is a proof of disorgani- 

 sation. But then comes in a new principle of connexion first, and unify 

 afterwards. The lines of pressure [are made prominent features ; the 

 compounded arches are distributed to their props ; the vaults are supported 

 by ribs; the ribs by vaulting shafts'; the upright meeting of the end and 

 side is allowed ; the structure is distributed into compartments according 

 to such lines, each of these being symmetrical in itself." — p. 15. 



If the admirers of Precedent, those who confound antiquity and excel- 

 lence as essentially synonomous, feel unwilling to admit the authority of 

 two eminent writers who characterise a large part of Roman architecture, 

 the one as discordant and dishonest, the other as incongruous and inevi- 

 tably transitional, let them reflect that the Komans were, until the time of 

 their emperors, so constantly engaged in foreign or domestic wars, that 

 they had little opportunity for cultivating the arts of peace, even if thay 

 had not lacked the desire and c; pacify ; that they never exhibited that 



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