Free Setting Foot on the Shores of Connemara by Tim Robinson Page A

at the lower levels by the pallid Viola persici folia , a rarity in Ireland, where it is almost restricted to this specialized station in life. In the centre, pondweeds grow in the muddy dregs around the natural drainholes.
    Sometimes in summer one finds that the empty bowl of a turlough is sheeted in what looks like whitish blotting-paper laid over the vegetation; I remember being baffled by the phenomenon when I came across it for the first time in the Aran Islands. It is made up of the matted and bleached remains of microscopic algae, which have multiplied countlessly in sun-warmed water and then been left high and dry when the turlough emptied. Algal paper, as it is called, can appear with mysterious suddenness; in Germany, where it has been recorded only about a dozen times, it is called meteor paper, as people imagined it had fallen from the sky.
    A bare limestone landscape without surface streams, in which the drainage is subterranean, is termed a karst, from the name of such a region in Yugoslavia. The Burren is a karst that has been worked over by glaciation; the bowls of these turloughs are depressions that have been gouged out by the glaciers, or are formed in deposits of glacial drift. Other karstic and glacio-karstic features of the Burren can be seen on the hillsides around Mám Chatha, such as, to the east of the pass, a row of steep conical pits which were once swallow-holes of some long-vanished stream, and a ravine formed by the collapse of a cavern excavated by water flowing underground. These impressive works of water date from a time when the shale strata that still overlie the limestone farther south were much more extensive than they are today, for erosion is slowly stripping them away. A stream running off the impervious shale will be acid with bog-water, and on reaching the limestone will soon ( i.e. over many hundreds of years) dissolve itself out a swallow-hole by eating away at the fissures and enlarging them; the rest of its journey to the sea will be underground, with perhaps some reappearances in turloughs and springs. As the area covered by shale contracts, the stream will abandon its first swallow-hole and punch through another one closer to the retreating boundary of the shale; one can see the process at work today around the margins of Slieve Elva (and it is because of their creative implication with the limestone topography that one must include such shale areas in the region to be thought of as the Burren). This is the location of the famous potholes and caves of the Burren, which the wet-suited experts can follow for, in one case, over eight miles. Their latest discovery has been of a section of dry cave near Doolin, which can only be entered through an opening on the sea-bed and a quarter of a mile of submarine passage; the river that formed this system must have been flowing when sea-level was much lower than it is now, perhaps at the end of the last Ice Age. For the family party on a Sunday outing there is Aillwee Cave south of Ballyvaughan, farther west along the ridge from Mám Chatha; here one can stroll through over quarter of a mile of tortuous caverns, sprigged with tastefully illuminated stalactites .
    Just east of the summit of the pass are the scars of old opencast mining of fluorspar, the glossy purple crystals of which can still be turned up in the spoil. Fluorspar is formed out of calcite (the pure white and crystalline form of calcium carbonate) by the action of hot fluorine gas, and the fact that at one time there were such fumes rising through the fissures here is part of the evidence for the existence of granite deep down under the limestone. In fact it seems that the Burren is underlain by an extension of the granite that is exposed on the north side of Galway Bay. Perhaps it was because of this solid basement that the limestone strata were so little disrupted by the Hercynian uplift, some 270 million years ago, that left them as a plateau with just a slight southwards