CONSTRUCTION OF TIIE BUILDING.

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gutter, thus complete, is attached to a flanged iron plate, bolted on to theedges of the box-gutters, so that the parallel lines of gutter may form a con-tinuous tie from the eastern or western ends of the Building to the transept, andso that, should the wood shrink in length, it may not pull apart and distort thesides of the box-gutters.

Three of the notches referred to as being cut on each side of the gutters, arelarger than the others, and on them bars of wood, 2 inches by 1-? inch, groovedfor glass on both sides, are notched down. These bars (shown at A, fig. 12 )form principal rafters, and, being set at a pitch of 2? to 1, are fixed to a ridge3 inches by 3 inches, grooved for glass on both sides. The angle at which theseare fixed being the one which Mr. Paxton, in numerous experiments, has foundto be best adapted to the construction of similar roofs.

One of the principal reasons which led to the adoption of eight feet and notmore, as the pitch of these gutters from centre to centre, was, that the distancefrom ridge to gutter-edge might be covered with the largest sized glass that couldbe conveniently manufactured in one length, and that by that means the unsightlyappearance, and frequently leaky condition, of joined glass, might be avoided.

The method of construction of a 24 -feet bay of this system of roofing is shownin fig. 13 , and from it the reader may be enabled to follow the description we areabout to give of the construction of a length of roofing.

Fig. 13.

Their connectionwith the roofing;

Reasons for fixingtheir pitch at 8feet

A 24-feet bay ofroofing;

The gutters, piincipal rafters or main sash-bars, and ridge being fixed in now constructed,place, the long edge of a sheet of glass, 4 feet 1 inch, by 10 inches, is insertedinto the groo\e of the principal rafter, and a sash-bar (shown in section at B,fig. 12), 1 inch by I5 inch, also double grooved, is then put on to the other