There are days when the cloud cover is so dense and hangs so low that earth and sky are within hand’s reach of each other. We are all familiar with that sense of atmospheric density and its emotional charge, especially here in Wales, and certainly in the Black Mountains, that no man’s land between one country and the other, or as Raymond Williams almost said, between two sets of others. And as I mentioned in my last post, the quality of light on such days offers a world viewed through an amber or yellow lens — which reminds us that in alchemy the colour yellow has a particular valence: it stains and infects, carries with it the suggestion of corruption, of pus and bile, of an insidious contagion.

I am curious about the Black Mountains as a site of alchemical experimentation, and in my novel The Blue Tent I explored that idea with a backward glance towards the 17th Century Welsh alchemist Thomas Vaughan.

We might think of the seasonal shifts as a kind of alchemy. These are sometimes startling, and provide entirely different perspectives of the same landscape over the course of a year; as here, in two photos of the Tal-y-maes bridge, in the Grwyne Fechan valley, taken in January and August respectively.

But I have noticed something else, over the years, which I am certain is not unique to my experience. I have discovered on many occasions that just because a path appears on the map, it doesn’t mean it’s there. On the other hand, and perhaps more pleasingly, there are paths that exist on no map. And there is something else too, that we might call phantom paths, or paths that go missing. In his book The Hills of Wales, Jim Perrin has written about this idiosyncrasy of the Black Mountains: ‘There are places here I have seen in the past and been unable to find again, as though they had disappeared from the land.’

You are in a place you’ve been a hundred times before, but it has somehow changed, been reconfigured in your absence, and the land laid out before you has taken on a different aspect, so much so that it feels like another place entirely. It’s almost as though there were a shadow version of these mountains, an alternative or parallel massif, that you access, unsuspecting, along a familiar path or track, and within minutes you are somewhere else; not lost exactly, just somewhere you hadn’t expected.

In this no man’s land of the Mynyddoedd duon, the geography is sometimes malleable, shifting: it is the geological equivalent, I think, of the brain’s neuroplasticity, which has been defined in the Journal Frontiers in Cellular Neuroscience, as ‘the ability of the nervous system to change its activity in response to intrinsic or extrinsic stimuli by reorganizing its structure, functions, or connections.’ That’s it: the Black Mountains as a human brain! It is kind of shaped like one, don’t you think? With the Grwyne Fawr valley forming the central furrow, the left side comprising Grwyne Fechan, Cwm Banw, Pen Allt Mawr and Pen Cerrig Calch, the right side comprising everything to the east — from Darren yr Esgob, across the Ewyas Valley, Offa’s Dyke ridge, the Cat’s Back etc. And what if it reorganises its structure by minute degrees according to the external stimulus of quantum measurement — or of human observation? The relief map on my bathroom wall now makes more sense: it represents the territory of the Black Mountains as a massive brain, through which we might walk, and, who knows, have our minds truly blown.