Part 140

=Trestles.= A trestle is composed of a cap about 15 feet by 9 inches by 9 inches, of four legs, of two upper and two lower traverses, and of four braces. The cap is notched 18 inches from the end, to receive the legs; the notch is 5 inches wide and 1 deep. The legs should be from 5 to 6 inches square; a shoulder is made to tit the notch in the cap; the spread is quarter the height. The inclination in the other direction about one-sixteenth. The leg is spiked, pinned, or bolted to the cap. The lower traverse is 5 inches by 1¹⁄₂ inches, and is dovetailed into the legs at about one-quarter their height from the ground. The upper traverse, which is nailed on the outside of the legs and against the cap, is 6 inches wide and 1¹⁄₂ inches thick. The braces are 4 inches wide by 1¹⁄₂ inches thick, and are spiked to the cap and legs. When trestles are to be placed on a soft bottom, a flat sill may be spiked under the legs of each side.

_Trestle Bridge._--When the water is less than 4 feet deep, the trestles may be carried to their places by men wading in the stream; an abutment is formed as for an ordinary bridge; the trestles are placed with their caps parallel to the abutment sill and about 13 feet apart. When the water is too deep or too cold to allow this method to be pursued, the bridge may be constructed as follows:

The abutment sill being placed, the first trestle can usually be placed by hand; the balks are laid and covered with chesses to within 1 foot of the trestle, a roller is laid on the bridge; on this are laid two beams, from 30 to 40 feet long and 6 or 7 inches square. The trestle is placed upright, with its cap resting on these beams, to which it is firmly lashed. The pontoniers bear down on the other ends of the beams, at the same time pushing until the trestle is rolled out to the proper distance; then they suddenly release the beams, dropping the trestle into its place. The flooring balks are slid out on the two beams, adjusted, and covered with chesses.

When a boat or raft can be procured, the trestles are placed with much less labor. The boat is brought alongside the last trestle placed; two balks are laid from the bridge, resting on a saddle, or the outer gunwale of the boat; the side of the trestle-cap is laid on the balks, the legs extending over the outer gunwale of the boat. The boat is pushed off by means of the balks until it arrives at the proper position for placing the trestle, which is then righted. If it has not good bearing on the bottom, it is hauled into the boat and the legs are cut to the proper length.

The bridge may be entirely built of round timber. The caps should be from 10 to 12 inches in diameter, the legs at least 6 inches, the balks 7 or 8 inches, and faced on the lower side where they rest on the trestles, so as to bring their upper surfaces on the same plane. The covering may be of strong hurdles.

=Treves=, or =Trier= (anc. _Augusta Trevirorum_). A town of Rhenish Prussia, on the right bank of the Moselle, 65 miles southwest from Coblentz. Treves derives its name from the _Treviri_, or _Treveri_ (which see). Their capital, _Augusta Trevirorum_, became a Roman colony in the time of Augustus, and ultimately became the headquarters of the Roman commanders on the Rhine, and a frequent residence of the emperors. Under the Franks, into whose hands it fell in 463, it continued to flourish. In 843 it passed to Lorraine; in 870 to Germany; in 895 back to Lorraine, and finally was united to Germany by the emperor Henry I. Since 1814, Treves has belonged to Prussia.

=Treviri=, or =Treveri=. A powerful people in Gallia Belgica, who were faithful allies of the Romans, and whose cavalry was the best in all Gaul.

=Treviso.= A fortified town of Italy, in Venice, 17 miles northwest from Venice. Treviso, the ancient _Trevisium_, was a free town under the Romans; and after the fall of the empire was conquered in turn by the Huns, Ostrogoths, and Lombards. Thereafter it was for a time independent, and at length, in 1344, voluntarily submitted itself to the republic of Venice.

=Tria Juncta in Uno= (three joined in one). The motto of the knights of the military order of the Bath, signifying “faith, hope, and charity.”