The track followed a devious path across the heath, which, viewed from near at hand, was more undulating than at first appeared. The track had been built to avoid the steeper gradients, but every now and then it ran upon a low embankment or through a shallow cutting. On either side the heath spread out, silent and mysterious, sometimes bare and sandy, with twisted pine trees standing above it at intervals, sometimes covered with low, dense thickets, in which the general silence seemed to be accentuated. When the line rose slightly to cross one of the lesser eminences, the Professor caught a fleeting glimpse of still water, the wandering arm of some unfrequented lagoon among the islands of the harbour. Behind him the sun hung low over the long range of the Purbeck hills, which changed from green and gold to blue and purple as the sun sank ever lower. Against them, the sharp outlines of the ruined Castle stood out clear cut like a beacon.