?50 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[August, 



stnictivc principles, if true, must be anti-Gothic; that to make 

 open roofs beautiful and truthful, all Gothic ideas must be relin- 

 quished, &c.,"have received from himself the reflection befitting 

 their unqualified expression. With res])ect to the remaining 

 portions of the critique alluded to, I may say, with the editor of 

 the journal in which it appeared, "that his arguments have not 

 convinced ourselves;" and then I will proceed to bring under notice 

 that key to the construction of this truly wonderful example of 

 carpentry which I ventured to advert to in this Institute six years 

 ago. It was, however, mentioned as one among a series, and the 

 prominence that will be imparted to it by thug receiving your 

 attention in a detached form will, no doubt, secure the removal of 

 any error it may contain, and the candid admission of any merit 

 it may possess. 



My observations went to show that the arch was not merely a 

 very grand ornamental feature, but that it was absolutely tlie 

 essential principle and weight-sustaining medium of the truss; 

 and should this hypothesis prove correct, the propriety of the 

 Gothic, or the compressible system of design in carpentry must, I 

 conceive, be admitted. 



Commencing, then, with the great arch rib, which in its section 

 is upwards of two feet each way, and spans the width of the hall, 

 we find, that dividing the curve from the springing to the apex 

 into three parts, the first of such divisions gives a point in the rib 

 at which it is intersected bv a massive liorizontal beam of nearly 

 equal dimensions with itself. This horizontal timber, called the 

 hammer beam, extends outwards to the foot of the rafter, and is 

 continued in tlie opposite or inward direction to the same extent, 

 so that if secured on a central pivot, this timber might be acted 

 upon as a scale-beam or lever of the first order, and if loaded 

 equally at both ends would remain in its horizontal position, while 

 tlie entire weight would be concentrated at the pivot and thrown 

 upon the supporting arch. If, taking the hammer beam as a base, 

 we draw a perpendicular line from the inner extremity, it will be 

 found to cut the rafter, or surface of the roof, just midway between 

 the foot and the ridge, and taking this rafter or surface line as the 

 hypotenuse, a triangle will be completed. 



This ti'iangle will be found to have an exact counterpart in the 

 upper half of the roof; but as the weight is proportionate to 

 the superficial area, it is only necessary to explain that this area is 

 divided longitudinally into two equal parts that under this divi- 

 sional line a ])urlin exists, upon which is collected the weight of 

 the upper half of the roof, and this weight is transmitted, by a 

 vertical post, to the inner end of the hammer beam. The lower 

 half of the roof discharges, in like manner, its weight on the outer 

 end of the same timber, and the equipoise is thus rendered perfect. 



If the accuracy of tliis much be conceded, I think but little re- 

 mains for discussion. The fitness of the skeleton for its intended 

 purpose once seen and admitted — the graceful adaptation of the 

 tracery, and minor arrangements for supporting the slighter parts 

 by aid from the stronger will be manifest, and especially so when 

 it is recollected that gravitation is not the only force to be resisted, 

 but that the powerful action of tlie wind, on so large a plane, has 

 also to be largely provided against. In tracing the history of these 

 roofs, I have formed the opinion that their type is found in the 

 stone gablets, or principals, employed in early halls, of which 

 Conway Castle affords good examples, and a specimen also exists 

 in the Manor House at Ightham, in Kent. 



Professor Willis lias remarked — " A small chapel at Capo di 

 Bove, about a mile outside Porta S. Sebastiano, Rome, figured by 

 Agincourt, has the roof entirely sustained by a series of pointed 

 arches, resting on corbels, and entirely superseding the usual 

 trusses." I have not met with this illustration, but by the kind- 

 ness of Mr. Railtou, I can supply its place by the drawing of a 

 chancel, in which he has carried the principle into effect. The 

 more ancient employment of such gablets may be further referred 

 to in the aisles of Hartlepool Church, Durham, where they exist 

 in a perfect state ; and of St. Peter's, Northampton, where the 

 remaining nortions clearly indicated (at the time of my visit a few 

 years since) their original use. The nave of St. Peter's Church, I 

 am inclined to think, had its roof supported by a series of such 

 gablets, above the alternate piers. The Church of San Miniato, 

 without the walls of Florence, has precisely this arrangement, ex- 

 cept that the gablet occurs over every third pier only; but in other 

 respects the quatrefoil plan of the pier, and the appropriation of 

 two of the group of shafts to the support of the nave arches (one 

 at the back for the gablet across the aisle, and the fourth in tlie 

 front, which is carried up on the face of the clerestory, for sup- 

 porting the arch and gable over the nave) are identical in the two 

 churches. 



Speaking of San Miniato, Mr. Galley Knight observes—" Large 

 arches are thrown at intervals over the nave, connected with 

 smaller arches, which are thrown over the aisles, at once assisting 

 to support the roof, banding the whole fabric together, and giving 

 it additional strength. ^^ lien these arches occur, the pillars are 

 exchanged for compound piers, one sliaft of which is carried up to 

 meet the arch above." 



At San Zeno, Verona (a Romanesque edifice, begun in 1138, and 

 finislied in 1178) every alternate pier is a massive collection of 

 shafts, with ai-ches crossing the aisles and nave, as in the above 

 instances. So striking indeed is the resemblance in these build- 

 ings to many of our own Norman churches, where we find shafts 

 carried up with no reference to the present roofs, and yet well 

 adapted to the support of such gablets as I have been describing, 

 tliat there seems good reason to conclude that such features were 

 at one time very general in this country, as well as abroad, and the 

 question addresses itself to the attention of those entrusted with 

 the restoration of our more ancient churches. 



Previous to the date of the M'^estminster roof, timber arches had 

 been applied in a form consonant to the general characteristics of 

 their date, as at Nursted Court, near Gravesend, and other places; 

 whether the hall of Rufus was entirely covered by wooden framing, 

 or had stone supports, the construction in wood of such a gablet 

 as we have been considering, was the task proposed to himself, 

 and, in my humble opinion, nobly performed by the architect of 

 Richard the Second. Of those indeed who, to prove the falsity of 

 its principle, refer to the distortion it has sustained in four centu- 

 ries-and-a-half, it may be fairly inquired, whether the many failures 

 in masonry warrant the denial of truth in the theory of the arch 

 altogether. The term " foliated" has been ably advocated as appli- 

 cable to the later wooden roofs, but in examples antecedent to the 

 introduction of foliations as a common aixhitectural feature, the 

 roofs were, of course, without that characteristic; and in modern 

 works where cusps are excluded, as in lancet buildings, they are, 

 I presume, still generally and properly omitted. Such unfoliated 

 roofs " possess," it has been said, " the merit of giving a grand 

 and church-like, though simple effect, without doing violence to 

 the genius of its material." They certainly embody, in an eminent 

 degree, the principle of rendering elegant the essential construc- 

 tive elements, and of avoiding adventitious parts for ornament 

 alone. 



In concluding these remarks, I will advert for a moment only to 

 the unfairness and futility of instituting comparisons between open 

 wooden roofs and stone groinings, unless they were equally suited 

 to our means, and depended for adoption entirely on choice. I am 

 far from insensible to the charm of "the fretted vault," but where 

 is an example as capacious as Westminster Hall, doubling, as it 

 does, the breadth of our widest cathedral nave? When wood, ap- 

 plied to the purpose of groining, is painted, and made to represent 

 stone, a deception is clearly practised; hut, regarding the arched 

 ramifications of a natural grove as the type followed in ribbed 

 vaultings, there would seem little impropriety in representing the 

 "fair branches and shadowy shroud" of the cedar fairly and osten- 

 sibly in timber. The subterfuges witnessed in the wooden groining 

 over parts of St. Alban's Abbey, York Minster, and other buildings, 

 are, doubtless, owing to the ponderosity of stone. The sacri- 

 fice of internal height, which many of our finest edifices have 

 sustained from the introduction of stone groining (and which would 

 bequite destructive of effect in buildings of wide proportion), lays 

 them open to the severe remark upon the sjdendid outer dome of 

 St. Paul's, of being "a mere imposing show, constructed at a vast 

 expense, witliout any legitimate reason;" for it need not be men- 

 tioned, that the groined ceiling never supersedes the ordinary 

 roof, and between the two there often exists a chamber of con- 

 siderable height, not only for the purpose of increasing tlie weight 

 of the walls, and their ability to resist the thrust of the groin, but 

 also to admit of building the latter under cover. The cost of the 

 centring alone for a stone ceiling would, probably, pay for the deco- 

 ration of an open roof; and the value of fair groining, if taken at 

 fifty pounds a square, which experience enables me to state as a 

 proximate sum, would place it quite beyond general application. 

 \\'hile economy therefore confines us almost exclusively to the 

 open form of roof, it is gratifying to experience the conviction, 

 that it is truthful in principle, and, when artistically treated, ca- 

 pable of displaying, in the fullest and most graceful manner, the 

 entire capacity of the building it covers. 



Jii'marks. — Jlr. Donaldson thought that Mr. jMorris h.id 

 confined his remarks somewhat too exclusively to the peculiarities 

 of construction in the rouf of U'estmiiister H.ill. He had not, in 



