exhaustive inquiry into the number of men that would be required to garrison them, upon their structure, positions, and numbers in this and other countries. But the historical, or rather prehistoric problem which they present does not end with the discovery of their original use, for it is difficult to understand, first, where the multitudes can have come from which sufficed to man such considerable embankments; and, secondly, where provision, and above all water, can have been found for such garrisons; for though, as we have seen, the dew pans will always furnish water in certain amounts, they would never have sufficed for the large numbers which alone could hold from half-a-mile to a mile of rampart and ditch. Associated with these old camps are the tumuli to be found throughout the whole length of the Downs, especially upon their main ridge. But the reader who is interested in such things must be warned against accepting too uncritically the evidence of the Ordnance Survey upon this matter. In the majority of cases it is right, especially with regard to the very interesting group of tombs just beyond the kennels at Upwaltham, above the Chichester road where it crosses the Downs at Duncton Hill; but there is at least one case, and there are probably others, where the heaps of material accumulated in the making of the roads have been erroneously ascribed to our prehistoric ancestors, and, if the present writer is not mistaken, there is an error of this kind marked upon the map close to the new London road which climbs Bury Hill on its way to cross the Downs at Whiteways Lodge. The complete isolation of these heights, their loneliness, and their wild charm, is enhanced by a line of towns and of villages especially dependent upon them and standing at their feet towards the south. The northern line of villages which lies just under their escarpment on the edge of the Weald, which we have described as being probably prehistoric sites, and which are connected by what has certainly been a prehistoric road, are not directly made by or dependent upon the Downs themselves. Their farmers are not usually large sheep farmers; their shepherds are few; their lives and their industries are those of the plain; their building materials are oak and plaster; their inhabitants but rarely climb the very steep hillsides immediately above them. The villages and towns to the _south_, on the contrary, owe their very existence to the Downs, and show in their every aspect the [Illustration: AMBERLEY VILLAGE] [Sidenote: THE SOUTHERN FORT-HILLS]