_Sterlings_, or _Jettées_, a kind of case made about a pier of stilts, &c. to secure it, and is particularly described under the next word, _Stilts_. _Stilts_, a set of piles driven into the space intended for the pier, whose tops being sawed level off, above low-water mark, the pier is then raised on them. This method was formerly used when the bottom of the river could not be laid dry; and these stilts were surrounded, at a few feet distance, by a row of piles and planks, &c. close to them like a coffer-dam, and called a _sterling_, or _jettée_; after which loose stones, &c. are thrown or poured down into the space, till it is filled up to the top, by that means forming a kind of pier of rubble of loose work, and which is kept together by the sides or sterlings: this is then paved level at the top, and the arches turned upon it. This method was formerly much used, most of the large old bridges in England being erected that way, such as London bridge, Newcastle bridge, Rochester bridge, &c. But the inconveniences attending it are so great, that it is now quite disused; for, because of the loose composition of the piers, they must be made very large or broad, or else the arch must push them over, and rush down as soon as the centre was drawn; which great breadth of piers and sterlings so much contracts the passage of the water, as not only very much to incommode the navigation through the arch, from the fall and quick motion of the water; but likewise to put the bridge itself in much danger, especially in time of floods, when the water is too much for the passage. Add to this, that besides the danger there is of the pier bursting out the sterlings, they are also subject to much decay and damage by the velocity of the water and the craft passing through the arches. _Thrust._ See DRIFT. _Voussoirs_, the stones which immediately form the arch, their undersides constituting the intrados. The middle one, or key-stone, should be about ¹⁄₁₅th or ¹⁄₁₆th of the span, as has been observed; and the rest should increase in size all the way down to the impost: the more they increase the better, as they will the better bear the great weight which rests upon them without being crushed; and also will bind the firmer together. Their joints should also be cut perpendicular to the curve of the intrados. For more information, see Professor Hutton’s _Principles of Bridges_, in 8vo. BRIDGE, in gunnery, the two pieces of timber which go between the two transoms of a gun-carriage, on which the coins are placed, for elevating the piece. See CARRIAGE. BRIDLE-_Arm Protect_, a guard used by the cavalry, which consists in having the sword-hilt above the helmet; the blade crossing the back of the head, the point of the left shoulder, and the bridle-arm; its edge directed to the left, and turned a little upwards, in order to bring the mounting in a proper direction to protect the hand.