1842.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



259 



The first section begins by pointing out the essential difference 

 between Roman and Gothic vaulting, the latter consisting of a frame- 

 work of ribs or stone arches, upon which the real vaulting is supported, 

 a mode of construction which the author designates as "rib and pane 

 work." In the early stages of vaulting, during the Norman period, 

 these ribs oifered very little geometrical diilicully, but as the number 

 of ribs was increased, a more artificial mode of structure became 

 requisite, and the investigation of the mechanical processes by which 

 the arch stones might be fitted to each other, so as to produce the 

 existing results, occupies the remainder of section 1. Among the 

 diagrams which illustrate this portion of the work are exhibited the 

 working lines left by the masons on the beds of the vmssoirs of ancient 

 arches which have' been taken down. In section 2, the first point 

 considered is the difficulty of adjusting the curvatures in groined vaults 

 when the springing and elevation of the lateral, transverse, and 

 diagonal arches are on the same level, but the spans different. In 

 circular arches this difficulty is accommodated by stilting them at the 

 imposts, or making the diagonal ribs a segment less than a semicircle. 

 With the introduction of the pointed arc!; this difficulty was greatly 

 diminished; " but notwithstanding the possibility of making pointed 

 arches of any proportion of height and span with their centres of 

 curvature upon the impost line, it will be found that the old expedient 

 of placing the centres of curvature above or below the impost line, 

 for the better adjustment of these arches, was still retained in pointed 

 architecture until the four-centred arch was brought in. I shall proceed 

 to examine this more at length, since it involves so much of the 

 characteristic appearance of these vault?." This characteristic 

 appearance in original Gothic vaulting arises from the curvature 

 of" the ribs, (as Professor M'illis makes it evident by numerous 

 examples,) being always arcs of circles, and he comments very justly 

 and severely on the erroneous but comujou method of jjrojecting 

 the diagonals of Gothic vaults by ordinates, to the ulter destruction 

 of the medieval character of the work — "This is the genuine prin- 

 ciple of the Roman and Italian groined vault, but is altogether foreign 

 to the principles of Gothic architecture, in which every rib should 

 spring as a separate and independent arch, and in which the elliptic 

 curves proAiced by this method are totally at variance with the 

 characteristic forms of the style." This mode of projecting the 

 diagonals was taught by De I'Orme, but he was perfectly aware 

 that it was inapplicable to Gothic vaulting, of which, as a matter of 

 curiosity, he gives a description, making every rib perfectly inde- 

 pendent of the rest in its curvature. This stupendous blunder is 

 therefore due to more modern times. Even in genuine Gothic vaulting 

 the effect becomes comparatively vapid after the introduction of the 

 four-centered arch, owing to the regularity with which all the ribs 

 start at the same angle from the impost. 



The third section is of great ] ractical utility, and treats of projecting 

 the forms of the stones in decorative vaulting, especially of such as 

 form the converging poiits of the Hemes. The subject is complicated, 

 and not to be made intelligible without refereiice to the diagrams by 

 which it is copiously illustrated. The Hemes in decorative vaulting 

 form a variety of elegant figures about the centre of the vault, of 

 which a star shape is the most common. Hence Professor Willis has 

 given to one class of this description of roof the name of slellar 

 vaulting, which very happily expresses its character. The depend- 

 ance of the designs of these vaults upon geometrical construction is 

 well illustrated, the form sometimes coming out in the solid when its 

 existence would hardly be suspected from a mere view of the plan ; 

 and on the other hand being sometimes symmetrically laid down, and 

 disappearing under the elfects of the perspective. As vaulting 

 advanced in complexity, a revolution took place in its mechanical 

 construction. This occurred when the compartments of Heme vaulting 

 became so numerous, and consequently so coi4racted, " that it was 

 found simpler and stronger to work the small [.ortions of panel sur- 

 face between the branches of the boss stones out of the same block, 

 than to cut them away and drop in the panel afterwards. Then the 

 bosses, from the increasirg complication of the patterns, began to 

 approach so close, that it was worth while to take the pains to make 

 them meet, and thus the crowns and ridges of the vaults came also to 

 be built solid. Lastly, the solid construction was extended to the 

 entire vault, and so by gradual degrees the mechanical and decorative 

 construction of the vault, which began by being identical, ended by 

 becoming totally different." This brings us to the subject of section 

 4 — fan vaulting. 



We must here ;.gain refer to the work and the diagrams, in which 

 is developed the method by which the complicated forms ol the stones 

 in these remarkable structures may be accurately modelled. The 

 characteristics of fan vaulting are thus described : — 



"The ]iattern of these vaults is always a kind of tracery of the 

 same class as the perpendicular tracery which at that period occupied 



the heads of windows or the surfaces of walls, the only difference 

 being that th.e mullions, instead of leing parallel and vertical, are 

 curved, and radiate from an impost. Instead, therefore, of the hori- 

 zontal transoms of windows, we have level circles intersecting the 

 ribs at nearly equal distances, and intermediate rays or ribs are inserted 

 between the princij)al ones. The panel spaces into which the surface 

 of the vault is thus divided are furnished with arch heads and foli- 

 ation, exactly as the similarly produced panels are ornamented in the 

 tracery of windows. 



"I have already stated that in the Heme vaults a star pattern is 

 commonly found, which radiates from each impost in the same way 

 as the fans of the present class of vaults. The difference between the 

 star and the fan is, that the star is formed of ribs, which mav be and 

 often are of different curvature, and the rays of the star of different 

 length, but so skilfully arranged with regard to their solid effect, that 

 although irregular upon the plan, this irregularity is not offensively 

 perceived in the complete work. 



"The fan is, on the other hand, formed of ribs strictly of the same 

 curvature and elevation, and its outline is bounded by a horizontal 

 circular rib instead of the zig-zag line of Hemes in the former vaults 

 by which the rays of the star are pointed. The effect of the fan is 

 that of a solid of revolution, upon whose surface panels are sunk; 

 the effect of the star is that of a group of branching ribs. This differ- 

 ence of character is assisted by the mode in which the mouldings are 

 disposed in the two cases. In the older vaults a vertical plane upon 

 the plan line of every Heme or rib divides it into two symmetrical 

 halves; but in the fan vaults the moulded rings and arch heads are all 

 perpendicular to the surface of the vault. 



" In fan vaults the quantity of decoration is so much increased, and 

 its parts become so small, that it is no longer practicable to frame the 

 tracery of these vaults on the rib and panel system with Hemes and 

 boss stones, and consequently the portions near the crown of the vault, 

 where the decoration is compressed and crowded, are always con- 

 structed of jointed masonry. But the branching ribs below the first 

 series of arch heads are still built of long stones filled in with panels, 

 and the tas dt charge from whence the ribs spring is also laid in level 

 courses as before. There are a few exceptions to this general de- 

 scription ; for example, the vault of Henry the Seventh's Chapel, 

 which, however, differs in many other particulars from these fan 

 vaults, and will be separately described. It is entirely constructed 

 of jointed masonry without panels. Also the vault of Islip's Chape! 

 at Westminster is a real fan vault, but without any mixture of rib and 

 pane! work." 



In illustration of this portion of the subject, the author has described 

 the vaulting of the chapel at the east end of Peterborough Cathedral, 

 the construction of which is identically the same with that of King's 

 College Chapel vault, on a smaller scale, but of very superior execution; 

 that of Henry Vll's Chapel ; and that of St. George, at Windsor, tlie 

 latter being not a real fan vault, but " a wagon vault, whose lateral or 

 transverse vaulting cells enter it below its crown." These descrip- 

 tions are accompanied by three elaborate engravings, exhibiting the 

 construction in tlie most perfect manner, by isometrical views of the 

 upper surfaces. There are also plans and sections of the same sub- 

 jects, and of the beautiful Heme vaulting in the cloister at Canterbury. 



An appendix adverts to some very striking effects produced by 

 modifications in the forms of the spandrils in the vaults of the cloister 

 at Norwich, upon which it is unnecessary to dwell, as the paper froui 

 which it is transferred was read lately, and reported in the Jounn ! 

 at the time.* 



We hope enough has been said on this admirable essay to recommend 

 it to all who profess the study of our mediaeval structures, whether 

 as architects or antiquaries. The information it contains addresses 

 itself to both classes, and if it were for the sake of this paper 

 alone, the volume ought to be in the hands of every one inte- 

 rested in Gothic architecture. We cannot conclude better than in 

 the author's own words, hailing with the most sincere satisfaction 

 the promise wliich he holds out. 



" In conclusion I must beg it to be recollected that I offer this paper 

 as a sketch of an investigation, for the completion of which 1 request 

 the assistance of the members of the Institute in the collection of 

 facts and examples. 1 have endeavoured throughout to show from 

 evidence the existence and employment of geometrical methods from 

 a very early period, and have attempted to restore some of these 

 methods. I have also ventured to assert the importance of certain 

 forms and arrangements in imparting character to the buildings in 

 question. The necessary limits of a paper of this kind have prevented 

 me from introducing several topics which may appear to belong to the 

 question in hand. Thus I have suid nothing respecting mechanical 



" See p. 9^— Journal for March, 1842. 



