Much of the surface, again, was occupied by hills or mountains separated by valleys or plains through which some 200 rivers--many of them far more powerful streams than they are to-day--flowed towards the sea. As for the nature of much of the soil of England, the early conditions are further recalled by Daniel Defoe who, in describing the "Tour through the Whole Isle of Great Britain" which he made in the first quarter of the eighteenth century, speaks of "the soil of all the midland part of England, from sea to sea," as "a stiff clay or marly earth" for a breadth of 50 miles, at least, so that it was not possible to go north from London to any part of Britain without having to pass through "these terrible clays," which were, he says, "perfectly frightful to travellers." {6}It was under conditions such as these that Britain obtained her first roads; and it was, also, conditions such as these that were to affect more or less the future history of inland communication in England, adding largely to the practical difficulties experienced in making provision for adequate transport facilities. Inasmuch as a great number of chariots were used by the Britons in their attempt to resist the invasion of Cæsar, it may be assumed that there were even then in this country roads sufficiently broad and solid on which such chariots could run; and though evidence both of the use of wattles in the making of roads over clayey soil and of a knowledge on the part of the early Britons of the art of paving has been found, the British chariot-roads were so inefficiently constructed that few traces of them have remained. The earliest British roads were, however, probably of the nature of tracks rather than of durable highways; and they may have been designed less for the purposes of defence against invasion than in the interests of that British trade which, even then, was an established institution in the land. Writing in "Archæologia," vol. xlviii (1885), Mr Alfred Tylor expresses the view that the civilisation of the Britons was of a much higher character in some respects than has till recently been supposed. From the fact that Pytheas of Marseilles, a Greek traveller who lived B.C. 330, and visited Britain, described the British-made chariots, he thinks we may assume that the Britons had discovered the art of smelting and working tin, lead and iron, and that they used these materials in the making both of chariots and of weapons. But they produced for export, as well as for domestic use. Tin, more especially, was an absolute necessity in Europe in the bronze age for use in the making of weapons both for the chase and for war, and the metallurgical wealth of Britain afforded great opportunities for trading, just as it subsequently gave the country the special importance it possessed in the eyes of the Roman conquerors.