It was in this period that Bracken began to perfect his peculiar—some might say unique—talents for exploration and route-finding. He already had an instinctive grasp of the strategy that distinguishes an explorer (able rapidly to establish his sense of place in a widespread system) from an orienteer, able to grasp only the minutiae of tunnel directions in a smaller area. The key to this strategy lies in getting to know the outline of a system before exploring its detail—which was what he was now doing with the Ancient System.
Bracken knew that there were two parts to the Ancient System—superficial summer tunnels which, on the edges, were bigger, forming an all-round peripheral system serving the central core; and a deeper, probably more ancient, set of tunnels, whose area was much more restricted and where food supply was likely to be a major problem except in the winter moleyears, when worms were driven deeper underground. He suspected that the big communal tunnel he had first entered from the cliffside formed a wide encirclement of the whole summer system, and this was soon confirmed by his following it from the slopes right round to the cliffside. It petered out, somewhat, further on, where it turned northwards on the west side and he did not bother to burrow his way through the many roof-falls in there. Instead, he pursued it back past the slopes and north of the Stone clearing where, again, it continued its circle round the whole system and faded again as it turned southwards. From this great circling tunnel there were several routes radiating into the centre.
First, he must find his courage and return to the deeper system where, though he dreaded doing it, he must make his way to the Chamber of Dark Sound and somehow past that long-dead mole.
But before doing that, Bracken decided—perhaps more as a way of delaying the day when he must go back to the deeper tunnels—to find out what tunnels lay between the summer communal route on the east side and the slopes beneath, to where, here and there, the present Duncton system reached. His objective, for he liked to have one, was to make his way to Hulver’s tunnels, for he was convinced that the sealed-off tunnels he had seen in them, and puzzled over, must lead up into the Ancient System. It was there, where Hulver himself had lived and had tried so hard to maintain a living link between the old and the new, that the physical link must lie. Bracken wanted to establish the fact of it before doing anything else.
It was in this period of a moleweek or so that Bracken began to perfect another of his strong talents for exploration and route-finding. His accidental discovery that a mole may use sound to make carved walls ‘speak’ had made him think about the possibility of using sound on ordinary walls in ordinary tunnels.
Of course, he already did this instinctively to some extent, using, for example, the echo-back of his pawsteps from a wall ahead to gauge how far he had to travel before reaching it. But until now Bracken had only done this in the tunnels he knew—and the soil in the Duncton system was too soft and absorbent ever to allow moles there to refine this technique very much. Up here, however, the soil was harder and much more responsive to sound and vibration, and now Bracken began to exploit the fact. He spent long periods trying different sounds on particular stretches of tunnels, learning to read the tunnel ahead from the sound it sent back. A straight tunnel running into a T-junction sent back a much clearer signal than a similar tunnel that had twists and turns; a tunnel with many burrows off it was more muted and richer-sounding than a similar tunnel with simple runs off it; softer soil—of which there were pockets on the Ancient System—was less responsive than harder soil and deeper sounds had to be used on it to get a maximum return of echo. Different sounds had to be used to maximise the information coming back from even clear-sounding tunnels—too sharp a sound, for example, in a responsive tunnel came back so fast and its echo repeated so often that it drowned itself in his own sound, and the information was lost.
So Bracken proceeded on his explorations, testing different sounds, trying out different thumps and scratches with his paws, and generally making enough noise to frighten a whole system of moles, let alone one, had they been there. But to Bracken it seemed that nomole would ever be there and, protected by his sense of isolation (though often regarding the fact of it as a curse), he went on in his humming, sounding, scratching, thumping way, turning the art of exploration into a science.
