If a special example be required of a road having grown up and remained on an uneconomic trajectory on account of marsh moulding its earlier history, one of the best in England is that of the Arundel road south of Pulborough. Seawards from Pulborough (a landing and crossing-place on the upper River Arun of great antiquity) the next considerable inhabited spot was the port and fortified spur of Arundel. The distance as the crow flies is a short day’s march or less, some ten miles. Now, the road could have been taken in a fairly direct line and everywhere upon the level had it not been for marsh. The marshes bordering the Arun prevented such a construction in early times: the road had to keep to a high, dry bank, then to climb right up to the top of the Downs and fall again upon Arundel. So it remained--having taken root--through all the advances in science: so it still stands to-day. The railway takes the obvious line, but the road, established centuries ago, remains on its former trajectory, climbs up many hundreds of feet, and then drops down again to Arundel, involving in the short distance of ten miles gradients of one in eight and heavy hill-climbing over more than half the distance. A neighbouring example of the extreme importance of _the first experiment_ in the history of a road is seen at Bramber, in the next valley eastward. There a similar situation--the approach landwards from the port of Shoreham--avoids the hills, because at some unknown but very early period a causeway was built at Bramber to negotiate the marsh; and that was because the isolated hill at Bramber afforded such a good opportunity of fortification and blocking the pass that a road was bound to reach it, and even under primitive conditions men were at the labour of making an embankment. [Illustration: Sketch II] iii WATER COURSES. The crossing of water courses does not seem to have been originally _in the main_ a search for a ford. It seems to have been rather a search for _good taking-off places upon either side, however deep the water in between_. The ford was used, of course, wherever it could be, and in it also the hardness of the passage under water was of even more importance than the depth of water: below, say, 4 feet. But the point to note is that often, and probably in the majority of cases, man in the early times took his short cut across water either by swimming or by taking advantage of floating material, and was much more concerned with the hard bank upon either side than with the depth of the stream.