Engineering Wonders of the World
Volume I

18 ENGINEERING WONDERS OF THE WORLD. THE PONT DU GARD .AQUEDUCT, NEAR NISMES, FRANCE. The greatest height is 180 feet. Length along second tier of arches, 885 feet. The lowest arches ate of 51, 63, and 80| feet span respectively. good means of communication, and whitherso- ever its armies penetrated the roads went with them. Even in Britain, the Roman “Ultima Thule” of Latin poets, Roads. we have many examples of the skill of the Roman road- maker, whose work was not equalled by his successors for many centuries, and is hardly to be surpassed by the product of the stone- breaking mill and steam-roller. We may criticise the uncompromising directness that characterizes the course of a Roman road— a directness that apparently scorned to turn aside to avoid a heavy gradient—but when we analyse the “ metalling ” of the highway, we can admire only. For the best class of road the engineer dug a shallow trench, 3 feet or so deep and 18 feet wide. The bottom he beat hard, and covered with large flat stones. On these he placed a layer of small stones ; on them again a course of concrete ; and finished the work with a surface of accurately jointed flat stones, sloping gently from the centre to the edges of the road to throw off the water. He also provided a kerb on either side, and a broad footpath for pedestrians. So well was his road made that in many cases it survived the neglect of the Dark Ages, and we could name localities where it still serves its purpose. As builders of walls the Romans had nothing to learn. They knew the secret of a mortar even harder and more tenacious than the stones it held together. Their bridges, too,