It is uncertain whether the Romans built any bridges of stone in Britain while they were masters of it; but, that they erected bridges of wood can hardly be doubted; yet the Thames and Medway were impassable at London and Rochester by any other means than ferries until about one hundred years before the Norman Conquest, when a timber bridge was erected at London, and it is hot improbable that at Rochester was built about the same time. These bridges being of timber, which of all materials used in building is most subject to decay, were afterwards rebuilt with stone, that at London in 1176, that at Rochester about the year 1386 or 1387. It is impossible to say with certainty how either of these bridges were constructed, though it is well known to those who have observed the progress of the various arts relating to architecture in this kingdom, that the earliest works of carpentry were very rude, their strength depending more on the quantity and substance of the timbers, than on the judicious disposition of them.