162 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[May, 



dent of some kind. The inquiry has confirmed me in my previous 

 belief, that the one at Salisbury was the lightest in construction of 

 this class. At York, the groining to the Chapter House is not less 

 deceptive than that to the nave and choir of the Cathedral itself, 

 being of wood, in one span, of 57 ft. diameter. Till lately, it was 

 enriched with painting and gilding ; it has, unfortunately, of late 

 years, been much injured by that worst vice in architecture, being 

 made to assume the appearance of a material it really is not. It has 

 been plastered and jointed and coloured in imitation of stone. With 

 a sort of prophetic dread of the march of desecration, the Rev. John 

 Drake, one of the Prebendaries, presented a view in 173 J, "lest time 

 or other cause should destroy or deface this magnificent structure." 

 The roof, which seems to be of very strange construction, almost with- 

 out any attempt at the principle of continuous trussing, has at least 

 the redeeming virtue of being held together by the tie beams. I have 

 been unable to get an accurate section of this building, which, how- 

 ever, is not of much consequence, as it bears so little on the object of 

 my inquiry. This Chapter House, which, I believe, was built in the 

 early part of the 13th century, would probably have been a few years 

 anterior to the Salisbury one.' The child certainly was not unworthy 

 of the parent. The Chapter House at Lincoln is not much more use- 

 ful to me, the excess of strength in this case being more puzzling. 

 The groin itself could never have required such buttresses, and we 

 can only imagine that the original roof must have been constructed 

 with some considerable degree of thrust, against which these immense 

 flying buttresses were brought into play. The present high pitched 

 roof, which was restored in 1S0O (one of low pitch having usurped 

 the place of its original one) must, if correct, occasion a considerable 

 thrust. This Chapter House is a decagon of GO ft. diameter, and is 

 supposed to have been the first built in tins country of polygonal form, 

 a variation from the square and oblong, as at Bristol, Glos'ter, Durham, 

 and Peterboro', supposed to have been suggested by the circular 

 churches of the Knights Templars. The Temple Church being dedi- 

 cated in 11S5, being 15 years before the completion of the Lincoln 

 Chapter House, Giraldus Cambriensis attributing it to Bishop Hugh, 

 who died in 1200. It undoubtedly must be considered a very perfect 

 work for so early an era. " St. Hugh was a native of Burgundy, and 

 may have obtained artists or designs from his own country." That 

 of Wells is an octagon of 57 ft. diameter, resting on a groined crypt, 

 Its height is considerably less than that of Salisbury, but like it, the 

 groin springs from a central column 3ft. diameter, surrounded by 16 

 smaller shafts, just doubling the size of the centre shaft, and the num- 

 ber of smaller ones at Salisbury. At first sight, the great dispropor- 

 tion between the abutments of this Chapter House and that at Sulis- 

 bury, seems unaccountable ; but on referring to the plan of the eroin- 

 ing, it will be found that this of Wells is much more elaborately 

 groined, and that the proportion of the stone ribs is as to 3, il ribs 

 springing from each buttress at Wells, 3 from each at Salisbury, 

 naturally adding considerably lo the weight and thrust even if the 

 intervening groin was not heavier. I am not aware of the material 

 used for this purpose. I believe chalk is not a material fuund in that 

 part of Somersetshire : it is in all probability of stone instead of the 

 lighter material. And in these causes, 1 think, the apparent discre- 

 pancy between the abutments at Wells and Salisbury may be satis- 

 factorily accounted for. I do not know the exact date of the building. 

 In feature and general delail it is of the s.une century as those I have 

 alluded to ; although in all probability it is subsequent to them. 

 Whether it has gained in effect by reduced height and lightness, I 

 must leave to others to determine. 



The Chapter House at Westminster, the last I shall speak of, is of 

 octangular form, and was a "remarkable instance of lightness and 

 richness of ornament." It was built in the reign of Henry III, proba- 

 bly about 1250. As at Wells there is a crypt, the groining of which 

 is of excellent workmanship. I believe that this building, in its ori- 

 ginal form, must have more closely resembled the Salisburv one than 

 any of those I have referred to; apparently of similar height and 

 width, its groin was originally supported by a central shaft having 

 eight smaller shafts surrounding it. The walls are not of greater 

 thickness than those at Salisbury ; and the projection of the buttresses 

 (where the flying buttress was not introduced) is as nearly as possible 

 the same as at Salisburv. These apply to those on the north-east, 

 north-west, and two to the west, where the cloister joins it. What 

 the character of the original stone groining was, I believe there is no 

 history remaining. Nor is it known exactly how long the monks held 

 it, but in 1377 the Parliament held their sittings there, the crown 

 having undertaken its repairs (well fulfilled) and it was so used till 

 1547, when Edward VI gave St. Stephen's Chapel for this purpose. 

 it was then occupied as a place of deposit for exchequer records. On 

 the 1th March, 1705, the House of Lords memorialized the Queen 

 (Anne) to have it put into repair, and this is stated to have been done 



soon afterwards by Sir Christopher Wren, though I know not where 

 are the existing traces of such repair. 



The springer of the groin still remains over the central shaft, and. 

 the boarded floor rests on the old encaustic tile. 



With the exception of this last instance, my consideration of the 

 polygonal Chapter Houses has led to little satisfactory result; and if 

 it were not that I fancy there is to be traced in each, good cause for 

 the variations we find, I might become a convert to Mr. Gwilt's belief: 

 "That the investigation of the equilibrium of arches by the laws of 

 statics, does not appear to have at all entered into the thoughts of the 

 ancient architects; experience, imitation, and a sort of mechanical 

 intuition, seem to have been their guides. They appear to have pre- 

 ferred positive solidity to nice balance : nor have they left us precept 

 or clue to ascertain by what means they reached such heights of skill 

 as their works exhibit." I think if Mr. Gwilt had remembered the 

 Chapter Houses of Westminster and Salisburv, he would have made 

 them exceptions to his rule, and have ailowed that at least they have 

 worked as close to " nice balance " as in these examples they could 

 well do. 



Having failed, then, to discover, in these works of similar form and 

 coeval date, any positive rules which could be a guide in determining 

 the question of sufficient abutment, I endeavoured to find, in the works 

 of those who have written on the theory of arches, some actual rule 

 which I could reduce to practise, applying to this case. In this search 

 I have not been very successful. The works of Peyronnet, Rondelet, 

 Gautier and other foreign writers on arches, apply generally to 

 bridges and other forms of vaulting rather than to groining as practised 

 by the early Gothic architects; and that their abutments would not 

 apply in one case is not very surprising when it is remembered that 

 "rib pointed vaulting," composed "ex lu^sde el lopho" has invariably 

 the actual rib thinner than the uniform thickness of the Roman vault; 

 and that the panels of the groin (the principal part in superficial 

 quantity) sometimes does not exceed one-ninth the rib in thickness. 

 A reference to their sections shows how light is the construction of 

 Lincoln and Salisbury Cathedral as compared with that of St. Paul's, 

 so much vaunted for the mathematical science it is said to display., 

 The naves of St. Paul and Lincoln are the same height and width ; 

 the piers of the towers are double the diameter of the shafts in the 

 latter, and its continuous wall exceeds in thickness by one-half the 

 wall and buttress of Lincoln. Nor have I found anything in the works 

 of Ware, Hutton, Mosely, Gwilt and others, which actually bears on 

 this case. In the work of Durand, an old French writer on arches, a 

 curious problem is laid down to determine the abutment of an arch, 

 which, if not based on the soundest laws of statics, is at least ingenious 

 and plausible, adapting itself to every form of architecture; ::ie 

 French engineers, 1 am informed, rely upon it to a great degree. I 

 pleased with its simplicity, that I determined to test it by an 

 experiment on a large scale. Having to construct the clerestory wall 

 of a church, which was 50 ft. high, to the wall plate, with semicircular 

 arches springing from columns 2 ft. 3 in. diameter, at a height of 

 18 ft. 6 in. from the ground, and abutting against a pillar, (of the 

 strength of which some doubts were entertained,) I had formed in 

 brickwork, to a quarter the full size, an arch of this description, re- 

 taining only as an abutment the width which this problem gave. The 

 arch was loaded i in proportion) to the full height of the 50 ft., and 

 no deduction was made for the openings of the triforia or for the 

 clerestory windows, which in the original, would much reduce the 

 weight over the crown of the arch. This experiment was made in 

 a foundation of very questionable nature; it was carried up in mor- 

 tar, and the centres were struck within an hour or two of its comple- 

 tion. This arch stood perfectly, and until the period of its being 

 taken down, some weeks afterwards showed no symptoms of weak- 

 ness. Having more abutment than this problem called for, and taking 

 into consideration the reduction of weight effected by the openings I 

 have alluded to, the clerestory walls were completed, as originally 

 intended, and stand perfectly. This, then, is the most theoretically 

 practical rule I have found, and has confirmed me in the belief that 

 the vault of this Chapter House, would stand perfectly with the 

 abutment it has. It will be found that the width of the abutment, at 

 the level of the springing, is in the case of Salisbury, about one-fourth 

 the span of the groin itself. That at King's College Chapel, Cam- 

 bridge, although of a much flatter and more thrusting arch, has the 

 thickness of the abutment only 3J times the width of the arch. 



Trinity Church, at Ely, has a stone vault of segmental form, which 

 has the abutments only one-fifth of the span of the arch, that arch 

 being of a very flat and thrusting form. Of these most complex the- 

 ories of the arch, so seldom brought to bear on individual cases, and 

 so seldom accordant, one is almost inclined to say with La Foutaine— 

 " Quand on 1'ignore, ce n'est rien, 

 Quand on le sait, e'est peu de chose." 



