The Zoologist/3rd series, vol 1 (1877)/Issue 4/The Natural History of Donegal

by James A. Mahony

 

THE NATURAL HISTORY OF DONEGAL.^[1]

 

[At a meeting of the Glasgow Natural History Society, held on the 30th January last, the following paper, entitled "Notes on the Natural History of County Donegal, with some Account of its Archæology," by Mr. James A. Mahony, Corresponding Member, was read. The paper was illustrated by an enlarged map of County Donegal, and was accompanied by lists of the phanerogamous plants and ferns, and of the birds of the district.]

A glance at a map of Donegal will show that it is a county of considerable extent, generally very hilly, and with a coast line of most irregular character. Lough Swilly, Mulroy Bay, and Sheephaven are arms of the sea penetrating southward from the Atlantic from twelve to sixteen miles, and modifying the climate so much that when snow falls, as it does very rarely, it never lies, but disappears in a very short time. These deep-sea fiords, with their rich marine fauna and flora, the coast outside beaten by the Atlantic surge, the numerous fresh-water loughs—many of them of considerable size—the bogs, mountains, marshes, sands, and cultivated grounds, present such a variety of conditions as is most favourable to the student of Natural History. I propose briefly giving some account of the Geology, Botany, Zoology, and Archæology of the district.

The primary and melamorphic rocks form the backbone of the County Donegal. In very local patches, and in small quantities, the more valuable minerals and metals occur. Lead, copper, silver and gold have been found, but so sparingly as would not repay the expense of working. The post-tertiary deposits are everywhere met with, and are often full of interest. The boulder clay is very general over the county, but, unlike its equivalent near Glasgow, it is a loose agglomeration of sand and hunch-backed pebbles and large stones. At Bloodyforeland it forms a cliff 110 feet in height, the matrix being a drab-coloured clay. Overlying the boulder clay in many places is a coarse gravel, highly charged with peroxide of iron; and where this is overlaid by the turf the stratum of gravel in contact with it is seen to be white instead of a reddish colour: this seems to be caused by the deoxidation of the iron by the organic matter in the turf. Bog-iron is to be found wherever the land is bleak and barren, and hundreds of tons of it are shipped annually to England, where it is used instead of lime for the purification of gas. Along the shores of Lough Swilly a light blue clay is found about forty feet above the present sea-level: it contains numerous fragments of shells, and seems to mark the old sea-beach. Bog is the surface deposit on a large portion of the county, and in some places it is as much as twenty feet deep, with trees occurring abundantly in it. In an island in the Rosses district the sea beats against a seven-feet cliff of bog, and in different places trees can be seen submerged, and the structures known as "smelting-pots," which were used some centuries ago for reducing iron, have been seen in three fathoms water. These facts point to a comparatively recent depression of the land, and this is apparently going on, although it is in no place so well marked as in the Rosses district.

The influence of plant-life in modifying geological conditions is not so often referred to nor so well understood as its influence in modifying climate. An instance of the former may be noticed. At Glassagh, in the district of Faunett, thirteen miles from Ramelton, the shores at one time were very sandy, and the kelp made from the seaweed cast in there brought only a low price; but some years ago the Earl of Leitrim planted all the bare sand above high-water mark with bent, which has held the sand together, so that now enough vegetable soil has been produced as permits of the growth of a sward composed of Viola tricolor, Anthyllis vulveraria, Erodium cicutarium, some of the coarse grasses and arenaceous mosses. The sand has been gradually disappearing, and the shore consists now of granite rock and beautiful pebbly strands, enabling the cottars to secure the weed free from sand, and to get the highest price for their produce. On the same Fannet coast the marine Algæ may be studied without much effort, as every tide washes in very perfect specimens of many of the deep-sea species, while the rock-pools are brilliant with Cladophoræ, Chylodadiæ and Polysiphonia, and an abundance of Codium tomentosum and Laurencia pinnatifida. The economic uses of the Algæ, described as useless by old Virgil, is well illustrated here in early summer. In May the old frond of Laminaria digitata becomes constricted, and is pushed off by the new frond, and the first storm drives in masses of this weed, forming often a bank four or five feet in depth: the natives call it "Scie weagh," meaning the May fleece, and the scene when it is coming in is an animated one. In one bay seventy carts may be counted, the horses up to the girths in the sea, and the natives forking up the precious crop. In the Faunett district, which has a coast of six miles, 8500 tons are secured, which, when dried, produces about 400 tons. From the beginning of August till the end of September is another busy time, when the "harvest weed" comes ashore: it consists of the variety stenophylla of Laminaria digitata, which is quite entitled to be ranked as a species, as it sheds not only its frond, but also a portion of the stipes, and its structure and chemical constitution are entirely different. Leaving the shore and going further west, one is struck by the abundance of the royal fern, which, instead of being the nearly extirpated rarity it is in the Clyde Valley, is here a common weed, growing in clumps like a little forest: it is disliked by the farmers, and, along with rushes and mosses, are all to be banished by drainage, "when the times mend." Ferns are not so specifically numerous as in Scotland.

In Marine Zoology there is much to interest and delight the student. At a short distance from the shore the boat glides over a stretch of Laminariæ-covered bottoms, where the large Eclimus spheræ may be seen prowling over the brown seaweed in the society of numerous star-fishes, shoals of Medusæ, and the beautiful zoophyte, Cydippe pileus, while multitudes of dogfish sport along the surface. The estuarine shores of Lough Swilly yield numerous species of Mollusca, while at Fort Stewart the whole littoral zone is covered with the shells of Anomia ephippium and Pecten striatus, and thousands of the valves of the oyster recall the days when that succulent bivalve could be bought here for threepence per hundred.

As for Mammalia, the Otter is too frequent. The Squirrel, Ferret, Fox, Weasel, Bat, and Hedgehog are often to be seen, and it seems to be quite true that there are no toads, moles or snakes in Ireland. The Black Rat (Mus rattus) is said to be found in an island in Mulroy Bay, but this requires confirmation.

Donegal can give a good account of birds, from the lordly Eagle downwards. The Golden Eagle has been often shot, and sometimes captured alive. The Peregrine Falcon and Merlin have been kept for long periods in confinement; and some have succeeded in making pets of the Barn and the Tawny Owl. There is a sufficient variety of song birds to keep up an interest in these charming neighbours. The Song Thrush (Turdus musicus) makes musical the dawn and gloaming from February till the middle of April: one fine performer which sings in a horse-chestnut in the garden brings flocks of the villagers specially to hear what they call the "Irish Nightingale." The Wren, Bullfinch and Swallow build about the houses, as do numerous Blackbirds; and in winter may be seen every day the Common Crane,^[2] the Waterhen, and the Cormorant, and sometimes the gleam of the Kingfisher may be marked in his swift flight up the stream. Wigeon, Teal, and Bernicle Geese frequent the muddy flats of the Swilly in winter, and are shot in numbers by those enthusiasts who choose to lie out all night in a flat-bottomed boat.

By the student of antiquity the County Donegal is held in reverence as the birth-place of St. Columb, and numerous are the legends connecting him with every hill and lough. The island of Tory is said to have been the scene of his missionary labours and miraculous exploits; but be that as it may, it is an island full of interest to the antiquary. Besides the old croms and round towers, which have been so carefully built that they resist effectually the climatic influences, and justify the poet in speaking of them as "the conquerors of time," the crannoges, or lake dwellings, which in the earlier periods of Irish history were preferred by the Irish chiefs to buildings on the mainland, are objects of great interest. The drainage of lands, which has been going on for the last few years, has revealed many of these old dwellings, long lost to sight, and at Portlough, four miles from Ramelton, one has recently been revealed which affords a fine example of the nature and uses of these settlements. The shell-mounds, which are common in the district of Faunett, are of considerable interest: they are invariably near the shore, above high-water mark, and are easily recognisable, even at a distance, by their rising eight or nine feet above the level sand. They all contain heaps of rough stones, which may be the remains of the hut, but the bulk of the mound is composed of shells of such edible mollusks as Littorina littorea, Patella vulgaris, Cardium edule, &c. Bones also of the cow, horse, sheep and pig are common, and are almost always split up—an entire bone is rare. These shell-mounds are less rich in remains than those of the Hebrides, and they cannot claim to be of high antiquity; that they are not of yesterday, however, is clear from the fact that on the shore adjacent no periwinkles or limpets can now be got, and the oldest inhabitant has no tradition of their origin. Their probable date may be the fifteenth or sixteenth century.

 

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1. See remarks in the "Occasional notes" of the May-issue of The Zoologist (Wikisource-ed.)
2. The bird here intended is the Heron, which in many parts of Ireland is called the Crane.—Ed.