214 On the Method employed to remove the Vaulted Roof of [April, 



buttresses, owing to the sinking of the side vaults, the whole was 

 found in such good condition, as to remove any apprehension as to the 

 firmness and stability of the main vault, &c. which being well support- 

 ed by the flying buttresses, and those of the outer walls, no external 

 shores were judged necessary ; and as in its construction it was 

 wholly independent of the side vaults, it was concluded, that notwith- 

 standing the shocks it might be expected to receive from their demo- 

 lition, yet that they might, when properly secured, be proceeded with 

 in perfect safety, without any fear of danger arising thereby to the 

 main vault. Accordingly, the only point which demanded immediate 

 attention was the counteraction of the imminent danger to be appre- 

 hended, from the further sinking and spreading of the side vaults, by 

 which, the main pillars in their shattered condition were liable to be 

 forced inwardly, and thereby to entail the consequent and sudden downfal 

 of the entire building. As this danger could only be prevented by 

 the construction of such massive shores on the nave side, which should 

 be able to resist every power that could possibly be exerted by the 

 spreading of the side vaults, the following plan of shoring, preparatory 

 to the removal of the side vaults, was adopted, andpursuedwithsuccess. 



Mode of shoring. — A solid bed of masonry (a) was laid for the firm 

 support of the foundation beam (b), upon the extremities of which were 

 fixed in mortises the uprights (cc) ; these were hollowed out to fit closely 

 to the main pillars, their base or lower ends being enlarged and 

 strengthened by the additional blocks (gg) to which they were firmly 

 joggled, and bolted, in the manner shewn. 



The straining beam (d) being then fixed at one end in the upright 

 (on a line with the shattered part of the pillars and strain of the side 

 aisles) by a semicircular tenon working in a similar mortice, the other 

 end cut to a tenon with a slight angle, was by means of three jack 

 screws (as shewn in the distance, forced up a smooth inclined mortise 

 well greased, cut in the opposite upright, and thus brought into a 

 horizontal position. The shores or struts (ee), let in obliquely upon 

 the foundation beam (b), were then fixed in the mortises cut in the 

 uprights, and straining beam (rf), and firmly wedged up into their places 

 and secured by the footsil (f) ; thus, the thrust of one aisle was brought 

 into play against the thrust of the other, and further spreading of the 

 side vaults effectually prevented. 



Centres for supporting the roofs of the side aisles. — The above work 

 having with great care and labour been accomplished, four strong cen- 

 tres or framings were next constructed, as shewn in fig. 2 ; which 

 wheu put together, were, by means of wedges underneath, brought 

 firmly up to the masonry of the vault ; and thus securely supported, the 



