1352

THEORY AND PRACTICE OF ENGINEERING.

Book II.

The eighth principle shows a different combination of bent timbers, where the framedvoussoirs are dispensed with, which sometimes are found objectionable, from the diffi-culty of making all the joints fit properly, and their liability to decay.

-7

q -

Fig. 2181. THE EIGHTH PRINCIPLE.

The ninth principle does not materially differ from the last; the pendant binding piecesare placed perpendicular, and do not diverge to the centre, from whence the bent timbersare curved.

Fig. 2182.

THE NINTH PRINCIPLE.

The tenth principle is a continual lattice, or open beam, so proportioned that it has beenmade to span very wide rivers in America .

Fig. 2183. LATTICE

m-U-U-lWJ-lUl ~U--U—U—LU U -Hf

The eleventh principle., called Long’s, does not consume so much timber or labour, and hasbeen much employed in America : it consists of a series of St. Andrew’s crosses between

LONG’S AMERICAN URIDGE.