Chapter VIII. Of three other Inventions, according to which wooden bridges may be made, without fixing any posts in the water

WOODEN bridges may be made, without posts in the water, like the bridge on the W Cismone, after three other manners; of which I would not omit giving the designs, because they are of a most beautiful contrivance, and may be more easily understood by every one who (hall have made himself master of the terms made use of in the said bridge on the Cismone; because these allo consist of beams placed cross ways, of colonelli, of cramps, and of beams placed long ways, that form the sides.

The bridges, therefore, after the first invention, are to be made after this manner: the banks fift fortified with pilasters, as necessity shall require, one of the beams that forms the breadth of the bridge is to be placed at some distance from them, and then the beams that form the sides, are to be disposed upon it, which with one of their heads are to lie upon the bank, and be fastened to it; after which, upon these, directly plumb with the beams placed for the breadth, the colonelli are to be fixed, which are to be fastened to the said beams with cramps of iron, and supported by the braces well fastened to the heads of the bridge; that is, in the beams that form the sides upon the bank: then leaving as much space as has been left from the said beam for the breadth to the bank, the other beam for the breadth is to be placed, and fastened in the same manner with the beams that shall be placed upon them lengthways of the bridge, and with the colonelli, and the colonelli to be sup-~ ported by their braces, and thus continue from one order to another, as far as shall be re quite. Observing always in such bridges these, that in the middle of the breadth of the river, there may be a colonello, in which the braces in the middle meet, and that other beams be fixed in the upper part of the colonelli, which joining from one colonello to the other will keep them united, and will form, with the braces in the head of the bridge, the portion of a circle, less than a semicircle. And in this manner, making every brace support its colonello, and every colonello support the beam for the breadth, and those that make the sides, whereby every part bears its own weight.

Bridges made after this manner, are wide at the heads, and grow narrow towards the middle of their length. There are none in Italy made after this manner; but conversing with Messer Alesssandro Picheroni, a Mirandolefe, he told me he had seen one in Germany. E, Are the braces, which being fixed in the beams for the length, support the

colonelli. ¥, Are the beams that bind one colonello with the other, and form a portion of a circ. I, Are the first beams, which at one end are Supported by the bank, and at the

other by the sir beams for the breadth, K, Are the second beams, which are supported by the first and by the second beam

‘bp y y

for the breadth. L, Are the third beams, which are Supported by the second and by the third beam

for the breadth.

And then there are these beams that form the breadth (as I have said) supported by the colonelli, to which they are fattened, and the colonelli by the braces.

The invention of the following bridge has the upper part, which is what supports all the weight, made of a portion of a circle less than a semicircle, and has the braces, that go from one colonello to another, so disposed, that in the middle of the spaces which are between the colonelli, they cross each other.

The beams that form the floor of the bridge, are bound to the colonelli with cramps, as they are in the above mentioned invention. And for a greater strength, one might add a g J 4 two beams at each end of the bridge, which being fastened with one end in the pilasters, and the other reaching under the first colonelli, they would help very much to support the weight of the bridge.

F, Are the beams placed under the bridge, at each end, that help to support the weight.

This last invention may be made with a greater or a smaller arch than it is here designed, Plate according to the quality of the site, and as the greatness of the river shall require. The height of the bridge, in which are the fences, or the braces that go from one colonello to another, must be an eleventh part of the breadth of the river. All the mortices that are made, ought, from the colonelli, to answer exactly to the centre, which will make the work very strong; and the colonelli will support the beams for the breadth, and for the length of the bridge, as in the abovesaid. The bridges, after these four manners, may be enlarged as necessity that require, making all their parts stronger in proportion.

E, Are the heads of the beams that form the breadth of the bridge.