Chapter VI. Of the Bridge directed by Julius Caesar over the Rhine

JULIUS CAESAR having (as he says in the fourth book of his Commentaries) resolved to pass the Rhine, that the Roman power might also be felt in Germany, and judging that it was not a very safe thing, nor worthy either of him, or of the Romans, to pass it in barks, ordered a “bridge, an admirable work, and most difficult by reason of the breadth, height, and rapidity of the river. But how this bridge was built, (although he describes it) is, nevertheless, not known, as the force of some of the words by him used in the de scription of it, is not understood; so has it been variously set down’ in designs, according to diverse inventions. As I have also thought a little upon it, T would therefore not omit this opportunity of setting down the manner of it, which T imagined in my youth, when first I read the said Commentaries, because it agrees pretty much (in my opinion) with C./esa words, and because it succeeds admirably well, as the effect has been seen in 2 bridge I have directed just without Vicenza, over the Bacbiglione,

Th is not my intention to confute the opinions of others, as they are all very learned men, and worthy of the utmost praise. For having left it in their writings as they understood it, and by means of their industry and fatigue, they have greatly facilitated the understanding of it to us. But before we come to the designs, I shall give the words of Caesar, which are these:

Rationem igitur pontif bane inflituit. Tigna bina fefuipedalia, panlulum ab io preeacut, dimenfa ad altitudinem fluminis, interval pedum drum inter se jungebat. Her cum machinationibus demissa in flue defixerat, fistucisque adegerat, non Juice modo direct ad perpendiculum, fed prona, ac acjajligiata, ut Secundum nature fluminis procumberent: bis item con aria duo ad eundem modum junta interval pedum quadragenum ab inferior parte contra aim atque impetum fluminis converse flatuebat. Ha utrague insuper bipedalibus trabibus ine missis, quantum eorum tignorum junttura distabat, binis utringue fibulis ab extrema parte dif tinebantur. Quibus difelufis, atque in contrarian parten revinétis, anta erat opens firmitudo, atque ea rerum natura, ut gio major vis aqua f¢ incitavisset, bac arétius illigata tencrentur. Hee diressa injecla materia contexcbantur, ac longurits, oratibusque conflernebantur. Ac nibilo ecus Jublica ad inferior parte fluminis oblique adigebantur, que pro price fubjecie, & cum omni opere conjunbx, vim fluminis excsperent. Et lice, 1tem Jura potent mediocr bath, ut fi arborum trunci, five naves deficiendi opens causa ¢sent & Barbarians misse, bis defenforibus, earum rerum wis minuerentur, new pont nocerent.

Tut sense of which words is, that he ordered a bridge in this manner. He joined two beams, each a foot and an half thick, two foot distant from each other, something sharp in the part below, and as long as the height of the river required; and having with machines fixed these beams in the bottom of the river, he drove them into it with a rammer, not directly plumb, but leaning in such a manner, as to be slanting according to the current of the water. Opposite to these, in the inferior part of the river, and at the distance of forty fot, he fixed two others, joined together in the same manner, slanting these against the strength and impetuosity of the river. Between these two beams he fastened other beams two foot thick, that is, equal to their distance from each other. They were held at each end by two braces, which being open, and bound contrary to each other, so great was the strength of the work, and such was the nature of the things, that by how much greater the strength of the water was, so much the firmer the whole kept braced together. These timbers were intermixed with other timbers, and covered with poles and hurdles. Besides which, in the lower part of the river, there were posts joined slanting, which were placed underneath instead of buttresses, and being united to the whole wor, served to refit the strength of the river. There were others also joined in the part above the bridge, at a moderate space, that in case trunks of trees, or ships, shou'd be sent down the river by the Barbarians to ruin the work, it might by these ramparts avoid their violence, and prevent them from hurting the bridge.

Th Caesar describes the bridge by him ordered over the Rhine; to which description the following invention seems to me very conformable, all the parts of which are marked with letters.

A, Are the two beams joined together one foot and an half thick, Something sharp in the lower part, fixed in the bottom of the river, not upright, but leaning

with the current, and two foot distant from each other. B, Are two other beams placed in the lower part of the river opposite to the above mentioned, and distant from them the space of forty foot, and slanting against

the current of the river. C, Are the beams two foot thick every way, that formed the breadth of the bridge,

which was forty foot.

1, Is one of the said beams. D, re the beans, which being open, that is, divided one from the other, and bound contrary to each other, that is, one in the part within, and the other in the part without; the one above, and the other below the beams, io foot thick, that formed the breadth of the bridge, and give so great a firmness to the work, that the greater the violence of the «water, and the more the bridge was

laden, so much the more it united, and the firmer it was. E, Are the beams that were put length-ways on the bridge, and were covered with

plates and burdens. T, Are the posts placed in the lower part of the river, which being slanting, and

Joined with the whole work, resisted the violence of the stream. G, Are the posts placed in the part above the bridge to defend it in case the enemy

Should send trees or Ships down the river to ruin it. K, Are two of those beams that were joined together, and not driven in the river

directly plumb, but slanting.

L, Is the bead of the beams that formed the breadth of the bridge.