60

CONSTRUCTION' OF THE BUILDING.

Box-gutters run-ning transverselyover trusses,

Connected longi-tudinally byPaxton gutters,& c.

The Paxtongutters;

Their details ofconstruction;

Their trussing;

the direction of from east to west. These timbers are introduced at intervals ofeight feet, being placed directly over the vertical standards of the roof trusses.

Between the top of the truss and the end of these timbers is placed a box(shown in section and elevation at C C C, fig. 7), running along the whole length,and attached to the upper flange of the truss, forming a gutter of considerablecapacity, for the purpose of carrying the water away from the roofs to the hollowcolumns, through winch it ultimately descends to the drains.

The peculiar form of the timbers, spanning from truss to truss, and the officesthey are called upon to perform, together with the fact that no less than 20miles of them are required for the construction of the roofing, render themworthy of a detailed description. They are now known as the Paxton gutters.The form of their section is clearly shown in fig. 9.

Figs. 9, 10, 11, 12.

Kg. 12.

§4 C

Kg. 11.

Fig. 10.

They consist of pieces of timber 24 feet in length, five inches wide by six inchesdeep. On the upper surface, a semicircular groove (C, fig. 9), lfth inch radius, iscut, in order to receive the external water from the roofs. On each of the twovertical sides of the timbers an oblique groove (B B, fig. 9) is cut, in order toreceive the condensed water, which, trickling down the inner surface of the glass,finds its way to these small channels, and is carried along them to their ends,where oblique cuts connect them with the box-gutters.

As the length of 24 feet would be too great for the gutter to carry itselfwithout bending, or, as it is technically termed, “ sagging,” the alternative pre-sented itself of either very much increasing the scantling, or contriving somesystem of trussing. The former was rejected on account of its heaviness andunsightly appearance; it was therefore determined that a rod of iron (shown atA A. A A, figs. 9,10, and 11) should be passed beneath the Paxton gutter, shouldbe secured to its two ends by cast-iron shoes (B, fig. 10), and should press up, ateight feet intervals in its length, two cast-iron standards (C, fig. 11), so as toeffect a camber or rise in its whole length of 2\ inches. So trussed, the gutteris capable of supporting no less a weight than 14 tons. A semicircular cut isgiven through the depth of the gutter at both ends, so that when two are placedend to end, the water may flow down to the box-gutters through a circular cavity.Twenty-seven notches are marked by a template, and cut on each side of theupper edge; a few of these are shown at DDD, figs. 10 and 11. The Paxton