] 835.] Account of the Roof of the Kdsipur Foundery. 113 



Each extremity of the tie-rods is bolted to a kind of shoe, (repre- 

 sented in figs. 5 and 6,) resting upon a stone slab on the wall, into 

 which the lower end on the iron beam abuts, (Fig. 1.) 



Fig. 2, is a plan of the roof, shewing the disposition of the frame, 

 planking and copper sheathing. In the section, Fig. 3, the longi- 

 tudinal rod is seen which steadies all the ties from lateral shake. 



Fig. 7, (a) shews on a larger scale the mode in which the longitu- 

 dinal tie-rods (a) are united by a bolt, (Fig. 8,) having two right-hand 

 screws, passing through the central coupling plates of the chains, and 

 the eye of the suspension vertex rod. This rod being firmly attached 

 by two bolts (b) through the beams at the vertex, any derangement 

 whatever of the roof, either vertically or horizontally, is effectually 

 prevented. At each end of the roof the longitudinal rods pass 

 through the walls, to which they are firmly fixed. 



Fig. 9, shews the horizontal overlaps of the copper sheathing, 

 which are cemented with white lead, and Fig. 10, the mode in which 

 the copper passes over the wooden battens fixed on the planks, to 

 which only the copper is fastened by copper rivets ; a copper cap or 

 ridge-tile lies over the whole length, to prevent the insinuation of 

 water at the fold : it answers this purpose so effectually, that the 

 roof was everywhere found perfectly water-tight, during the late heavy 

 season of rain, the first it had experienced. 



The Kasipur roof was set up without the assistance of any scaffold- . 

 ing from below. An experimental truss of timber supported on 

 chains, having been previously made to shew the advantageous ap- 

 plication of iron chains instead of tie-beams of timber to roofs of 

 so large a span, it was converted into a platform, moveable upon 

 wheels along the top of the walls, upon which by means of a crane 

 fixed at one end of the frame, the iron beams and every thing else was 

 easily and expeditiously raised and fixed ; the beams, &c. for the op- 

 posite side of the roof being passed upon wheels across the platform. 

 The whole frame-work was put up in 20 days. 



Before closing our short account of the Kasipur roof, we must notice 

 a curious optical deception, for which we are somewhat at a loss for a 

 correct explanation. On entering the room and looking up at the 

 roof, it strikes every beholder that the roof has somewhat sunk, and the 

 horizontal tie-rod is about five or six inches lower in the centre than 

 near the walls. So firmly impressed were we of this being the 

 case, that standing at one end of the room, and holding two flat brass 

 rulers, overlapping one another before the eve, we could readily mea- 

 sure the apparent angle of the tie-rod by raising the ends of the rulers 

 so as to coincide with the two halves of tie-rods On mounting the 



