I first came across the term black earth when reading Maud Cunnington's description of what was found at The Sanctuary, or rather, Maud uses the term a 'dark humus' to describe what is probably the remains of decayed turf.
The term black earth was used originally by her husband's great grandfather: William Cunnington (1754 – 31 December 1810) . His sketch plan of the long barrow in Heytesbury North Feild records a circular mound at the east end composed of black earth mixed with sarsens, flint nodules and chalk. This black earth puzzled both Cunnington and Wyndham (on whose ground the long barrow lay).
To check out his suspicions, William Cunnington consulted some chemists, Mr Hatchett and Dr Gibbs who told him that the black earth wasn't a result of fire, and that it wasn't animal matter...Richard Colt Hoare concluded therefore that it must be plant matter. Yet the black seemed too black for Cunnington and controversy raged over whether it was black like the pudding... because of blood...or not.
In 1889, William Cunnington (the grandson of the original W Cunnington) in his Notes on Bowl's Barrow describes what he learnt about the black earth. William followed his grandfather's example and sent some black earth off for chemical analysis. The report stated that ammonia had been detected. Ammonia is the breakdown product of proteins such as blood and muscle and it will happen with or without air present, but it seems that plant material doesn't produce ammonia in anaerobic- airless, packed inside a long barrow- conditions.
William Cunnington grandson believed blood to have been shed at prehistoric sites proving barrows to be sites of ritual sacrifice..
One detail that comes from William Cunnington senior's records is that long barrows, not always but often follow a sequence of black earth, a pit and a pavement (a layer of flat stone) and then a cairn or mound. Sometimes there is evidence of burning, and most have their wider end pointing eastwards.
At Bowl's Barrow, Cunnington found a pavement of flints nodules. Bodies had been laid out in no particular order on top of the flint pavement, by the side of the pavement Cunnington describes a cyst, or a pit neatly cut into the chalk- but he didn't have time to investigate this pit thoroughly as the whole structure of the barrow was becoming unstable.
Stones of sarcen and flint had been built up from the pavement to make the long barrow over the pavement almost 2m high, and the whole lot was capped with chalk to make a white mound.
The name black earth is redolent of darkness and mystery. The modern etymology of the word alchemy links it with Al-Khemet meaning Egypt, land of the black earth. The inundation of the Nile producing rich and dark and fertile soil.
But I'm not sure if this is simply a short-cut from information related by Madame Blavatsky.
Madame Blavatsky (1887) mentions this theory about Egypt but goes on to say that the word alchemy probably comes from Arabic al-kimiya meaning something that can be changed.
I have no idea either way!
Here's the whole thing- from Isis Unveiled:
I don't suppose William Cunnington meant anything of the sort when he became fascinated by the black soil inside barrows.
So let's assume that the black earth is freshly cut turf. The ground from which it was cut could be white? I'm thinking of those chalk horses cut into the downs, of how the ground is pale and full of bone-like flints. The bright green turf cut from the ground becomes a sacred area ringed around by the white ground.
Next there is the pavement of flints and the digging of a pit.
Next bodies go on top of the flints and the rest of the barrow is constructed.
But not all long barrows contain bodies; some contain lots, some only one. Most point eastwards: if it's the full moon being used as a marker, the most north-easterly full moon rises in December. The most easterly new moons are in early summer. It wouldn't be easy but if you wanted to know roughly what the season was, the moon could work.
But looking at the plants and trees would probably give you more of a clue!
So midwinter full moon as the time for the dead still makes more sense to me that the midsummer party stuff. But it is still the equinox that intrigues me- when the gates of the sun and moon open at the same time...