1879.] on the Logic of Architectural Design. 95 



has been often supposed to have arisen from a mere sentimental pre- 

 ference for the form of the pointed arch. But architectural styles 

 have in their growth and origin little to do with sentiment ; the 

 sentimental interest is projected back upon them from our own feelings. 

 So completely is this idea of the sentimental origin of the pointed arch 

 contradicted by fact, that in buildings of the Transition period, such 

 as Kirkstall and Fountains Abbeys, wo actually find the larger arches 

 which carry the main structure pointed, and the smaller ornamental 

 arches in higher parts of the building circular; the necessary conclusion 

 being that the round arch was preferred and the pointed form only 

 used in the larger arches for constructional reasons. But the main 

 value of the pointed arch to the mediaeval builders lay in the fact that 

 by its use the difficulty of intersecting vaults of different spans was 

 got over, practically at least if not quite theoretically. As will be 

 seen (at 12c), the use of the pointed arch enables us to build arches 

 of varying widths and of the same height, and having a curvature so 

 nearly similar as to render it practically easy to treat them as inter- 

 secting arches without an unsightly twist of the intersecting lines ; 

 and what little difficulty there would have been in securing the neat 

 adjustment of the two curves was obviated by the introduction of the 

 " vaulting rib " at the angles of intersection of the curves (13), on either 

 side of which the curves of the vaulting surfaces, divided from each 

 other by the deep and strongly-marked mouldings of the rib, could be 

 adjusted as far as necessary to harmonize with the curve of the rib ; 

 and this introduction of the vaulting rib, and the aesthetic prominence 

 given to it in the design, constituted a perfectly logical treatment, for 

 it represented the real construction of the Gothic vault, which, instead 

 of being, like the Eoman vault, an intersection of two arched surfaces, 

 became in reality a framework of arched ribs, between which the 

 vaulting surfaces were carried, the ribs assuming the real constructive 

 function (Fig. 14). 



Only one practical difficulty remained in designing a vault, a very 

 slight one, but which had important results in determining the latest 

 and in some respects most beautiful form of Gothic vaulting. This 

 difficulty arose from the fact that the vaulting ribs near the springing, 

 where they come down on the top of the capital, had to be run into 

 each other (" mitred ") in order to collect them on the small space of 

 the capital from which they were to appear to spring. And as the 

 ribs were still of varying lengths and curvatures and left the capital 

 at different angles, their adjustment so as to break off from each other 

 symmetrically and at the same height w^as a matter of some difficulty 

 and necessitated a good deal of humouring of the vaulting lines at 

 this point. The invention of the fan vault, the effect of which is so well 

 known in King's College Chapel and Henry VII.'s Chapel, got over 

 this defect, and rendered the whole perfectly logical. By intercepting 

 all the vaulting ribs by an arc of a circle {jplan. Fig. 15) at their highest 

 points, instead of letting them all run up to the ridge of the roof, they 

 were all reduced to precisely the same length, could all have the same 



