One hot August afternoon, a motor-boat, with a little dinghy in tow, was thrashing its way up a narrow, winding river in Southern Wessex. The stream, swollen by the drainage of overnight rain from the high moors that loomed in the hazy blue distance, was running riotously, casting buffets of spray across the bows of the little craft, and tossing like a cork the dinghy astern. On either side a dense entanglement of shrubs, bushes, and saplings overhung...