Country diary: the Trickle’s white witchcraft turns everything to stone

Welburn, North Yorkshire: A spring from the lime-rich bedrock calcifies all in its path, from pine cones to snail shells

January has wrapped itself so tight around the valley that there is no view today. Even the short sightlines in the woods are cloaked and murky. The mud on the main track is tedious, so I'm tempted by the firmer footing of a leafy badger path. It starts well but soon becomes steep and hostile, with bramble snares every few paces. The hulk of a dead birch gives way as I grasp it for support; muddied and disheartened, I try to cut back.

I emerge instead in the swamp landscape of a dinosaur picture book, thick with dead horsetails banded bone-white and brown like okapi legs. A few more squelching steps and I reach what must be the source of the small spring we call the Trickle. Here, its early course runs white over a petrified woodland floor. Bathed in water sprung from the lime-rich bedrock, twigs, leaves, pine cones and needles are turning to stone.