So it was with the Romans in Britain. They formed colonies in various places and built towns all over the land; they had country villas dotted here and there, some little distance from the chief towns, and built strong military stations in suitable districts. These posts were kept in communication by means of good roads. To trace out the network of Roman roads is a study in itself, and much has been learned therefrom. Some roads are still quite easy to trace, as far as their course is concerned, for many of our great main roads to-day run upon the top of them; and from time to time, when excavations are being made for sewers, or for laying water-pipes, or tubes for trunk lines of telephones, the actual metal and foundations of the Roman tracks are found, many feet below the present level of the road. It is sometimes stated that the Roman roads were always straight, and that all obstacles were cleared to make room for them. Whilst it is quite true that this "straightness" and directness was one of the characteristics of these roads, the makers of them were skilled engineers, and they not infrequently found that some older trackway, not particularly straight, was better suited for their purpose, as it avoided some of the natural difficulties of the country. When they used these older ways they took care to raise the surface and lay the metal on firm foundations, so that the traffic along them could be as rapid as along the new, straight roads--and the Romans were great people for getting about rapidly from point to point. One of the most frequent deposits of "rubbish" which the Romans have left behind is "oyster shells", often met with in quantities. They are found in places many miles away from the river-mouths where the oysters were cultivated; so that the question arises: "How did these shells get there?" Either they must have been brought very rapidly from the coast far inland, or the eaters of them did not mind eating them when they were very "high". At any rate, there the shells have been found, showing that distance was no obstacle in the way of getting, not only the things which they reckoned to be necessaries, but expensive luxuries as well. Although the main Roman roads are still in use, there are a great number of cross-roads, which for centuries have been out of use, and their exact courses can only be traced with difficulty, passing as they do through what are now quiet, secluded places, long overgrown by grass and underwood and cultivated fields. Many Britons must in the course of time have adopted Roman ways and Roman civilization; but the bulk of the Britons, living away from the Roman centres, kept to their own customs, and cultivated the ground in the way their ancestors had done. They prospered, on the whole, as the Romans kept the various tribes from quarrelling with one another.