When a Roman road was made, the first thing done was to mark out its course by the digging of two parallel ditches. This course was from 15 to 21 feet wide, and on it as the _gremium_, or foundation ground, was placed a layer of large stones 5 inches deep. This, known as the _statumen_, was followed by a fifteen-inch layer of broken stones cemented with lime. The _rudus_ thus formed was succeeded by the _nucleus_, a similar layer 10½ inches thick and constructed of small fragments of brick and pottery. Last came the _pavimentum_, made of large irregularly-shaped blocks of very hard stone fitted together and cemented with lime so as to form a perfectly even surface. The pavimentum was 5 inches thick, thus making a solid road raised about 3 feet above the level of the surrounding land. [Illustration: SECTION OF A ROMAN MILITARY HIGHWAY.] Such was the usual method of construction of a Roman highway. Where the natural surface of the ground passed over was hard rock, the two lowest layers, or _strata_, were dispensed with; but where no safe natural foundation existed, the labour was increased by the driving of piles into the soft ground to afford this. Over hill and down dale were constructed these wonderful roads. No obstacle save an impenetrable marsh or an unbridgeable river baulked the Roman engineer; and the outward distinguishing mark between the Roman road constructed sixteen centuries ago and its modern successor is often the fact that whereas the latter goes round a hill, and thus makes things easy for the traveller, the former climbs in a straight line right over the summit. What engineering skill the Romans must have possessed to build their roads! Straight from one military station to another miles distant over the hills did they succeed in driving their road. How did they judge its direction so accurately? We know not. And what immense labour was needed for the construction of their roads! Think of the cohorts of Roman soldiers engaged in building them, and of the slave-gangs of Britons toiling under the lash of the task-master as they quarried the materials for the use of the soldiers working many miles away. So hard was the work of the Roman soldiers in Britain, we read, that they ‘wished for death to relieve them from their insupportable toil.’ But human life stood for little in those days. What Roman engineer cared whether thousands of lives were spent in the making of his road? His one concern was to build it in such a way that for centuries to come the Roman legions should be able to march, and the Imperial Post to ride, along its hundreds of miles at the greatest possible speed. One hundred and sixty-five English miles were covered by Caesarius, a Roman magistrate, in the space of one day on a journey from Antioch to Constantinople, the whole distance of 665 miles taking less than six days. There is little wonder that Rome had become ‘Mistress of the World.’ * * * * *