It was only when a horse damp to its flanks passed us that I looked again at the map and realised that our circular walk included a ford. And that, despite the dry weather over the past few weeks, it was far too deep to contemplate attempting fully clothed. So our walk was aborted and, instead, we scrabbled along the banks of the Coquet (encountering my first nettles of the year in the process) in search of the cup and ring marks that our Ordnance Survey map told us were nearby.
The lower River Coquet near Morwick. The sandstone cliff with the cup and ring marks is on the left.
Even though we had a map reference and some field notes from The Modern Antiquarian website we still ended up staring at a nondescript sandstone cliff for some time before our eyes adjusted and we started to pick out the patterns on the rock. In particular, there was one set of three very clear marks – each a central depression surrounded by three concentric rings etched into the rock. They were just a few centimetres across but they contain all the mystery of Stonehenge: who carved them? When? And what for? You can find similar marks on rocks all over northern Britain, elsewhere along Europe’s Atlantic fringes and into the Mediterranean. Others in Northumberland have been dated to the early Neolithic (4000 years ago) but the reason why someone without metal tools put in the effort to create these marks remains elusive.
Left hand image: the cup and ring marks on the cliffs overhanging the Coquet at Morwick; right hand image: the dark brown patch is the seepage on the cliffs dominated by blue-green algae.
We were contemplating these questions as we sat on rocks beside the river eating sandwiches when I noticed the seepage running down the cliff a few metres away from these marks. Once again, an apparently bare (albeit damp) sandstone cliff revealed itself to the prepared mind. Close up, the damp surface is pockmarked with tiny hummocks, just a few millimetres across and, when you look closely, with a distinct green tinge. The prepared mind, however, had forgotten to bring any forceps or bottles, so I had to scrape off some of this film with a fingernail and wrap them in the clingfilm that had held my sandwich.
Upper image: a close-up of the seepage from the cliff at Morwick; lower image: cells of the blue-green alga Gloeocapsa from the seepage. The scale bar represents approximately one centimetre in the upper image and ten micrometres (1/100th of a millimetre) in the lower image.
Under the microscope this film turned out to be a mass of blue-green cells, each encased in a colourless sheath. The cells belong to a genus called Gloeocapsa and the thick sheath presumably offers some protection on those occasions when the seepage dries out. Like Phormidium we met in the previous post, Gloeocapsa is a blue-green alga, one of the most primitive types of organism. Though early microscopists classified them as part of the plant kingdom, we now know that they are actually bacteria, reflected by the formal name Cyanobacteria.
It is likely that Gloeocapsa, or organisms very similar to this, have inhabited damp habitats like these cliffs since the Precambrian. Indeed, they might have been here as the Neolithic craftsmen painstakingly carved the cup and ring marks which lets us put them into context. It is about 400 years since Shakespeare wrote Hamlet. We have to multiply this time span by 10 to get to the Neolithic period, about 4000 years ago. However, we then need to multiply this figure by 16250 to get to the Cretaceous period, when dinosaurs were common (65 million years ago) and then multiply this final figure by eight to take us into the Precambrian. In other words, the 400 years between the Elizabethan period and today needs to be repeated one million three hundred thousand times to take us to the dawn of biological time. And, for this entire period, organisms very similar to Gloeocapsa and Phormidium have been here.
Time, which antiquates antiquities, and hath an art to make dust of all things, hath yet spared these minor monuments …
(Thomas Browne, 1605-1682)