This bridge was built with piles driven down into the sand, which supported a flooring of timbers.

Caesar, considering it quite an exploit thus to bridge the Rhine, wrote a minute account of the manner in which the work was constructed, and the description is almost exactly in accordance with the principles and usages of modern carpentry.
[Sidenote: System of posts.] [Sidenote: Their great utility.] After the countries which were the scene of these conquests were pretty well subdued, Caesar established on some of the great routes of travel a system of posts, that is, he stationed supplies of horses at intervals of from ten to twenty miles along the way, so that he himself, or the officers of his army, or any couriers whore he might have occasion to send with dispatches could travel with great speed by finding a fresh horse ready at every stage.

By this means he sometimes traveled himself a hundred miles in a day.

This system, thus adopted for military purposes in Caesar's time, has been continued in almost all countries of Europe to the present age, and is applied to traveling in carriages as well as on horseback.

A family party purchase a carriage, and arranging within it all the comforts and conveniences which they will require on the journey, they set out, taking these post horses, fresh at each village, to draw them to the next.