Come autumn, the hills in Scotland look as empty of snow as anywhere else in Great Britain. And yet, there are some special places hidden from view where winter stubbornly hangs on despite the passage of summer. And, quite unexpectedly, the snow that falls in those places only rarely melts. These long-lasting ghosts of winter, which vary in size from mere pin pricks to enormous things the size and volume of buses, are Scotland’s famous snow patches. They’re a source of fascination and curiosity for most folk who wander the hills during the warmer months, and I’m no exception. I’ll…