The remains of human handicraft, in the form of log-houses or lake-dwellings, have been found buried under each and all these peat growths: a depth of 25 feet had overgrown the log-house discovered at Inver, Co. Donegal, and on the floor-level, outside the building, were traces of the corkers of the great oak forest age. It is practically impossible to estimate the rate at which a bog grows: if there be a fall, and consequent drainage, it will increase but little, whereas an undrained bog augments with considerable rapidity: so many contingencies are thus introduced as practically to invalidate in a great degree calculations regarding the growth of peat over prehistoric or other remains. G. H. Kinahan has estimated that in undisturbed conditions each year’s growth, represented by a layer or lamina somewhat resembling the markings on a forest tree, would average one hundred laminæ to the foot in white or surface turf, two to three hundred to the foot in brown turf, and six to eight hundred to the foot in black turf, so that the accumulation of 25 feet above the log-house at Inver, according to this painstaking calculation, would represent an age of startling remoteness.
Lakes.—Ireland was a land of lakes as well as of forests, for the white-shell marl, which forms the substratum of peat bog in low-lying situations, was formerly covered by water, till gradually displaced by the encroachments of the surrounding bog. Many of the smiling districts of to-day were then covered by water—
“Now land, now lake, and shores with forest crowned.”
Lakes were thickly scattered over the face of the country—lakes of irregular shape connected by stagnant shallows—the majority of small size, half marsh, half water, fringed with forest, and abounding in fish: The axe of the primitive pioneer and the modern engineers’ spade have revolutionized the aspect of the landscape: this process however was gradual, the forests were only driven back little by little, and it is comparatively yesterday since draining operations on a large scale have been carried out; within the memory of persons still living there were numerous localities throughout the kingdom, where
“The bittern’s lonely boom was heard
Along the waving reeds.”
It is only after drainage on a great, or rather thorough scale, that anything like complete inspection of the original structure of a lake dwelling, or any extensive “find” can be hoped for, the majority of such sites being surrounded by soft pulpy bog to such a depth and extent as to bewilder the most enthusiastic explorer.
Lough or Loch is the term applied both in Ireland and Scotland to a lake: it also signifies an arm of the sea. The shores of small sheets of water, and marshes with sedge-grown borders, were generally surrounded by bog, and the annual growth of this latter substance gradually encroached on the lake, till its former shining surface was changed into a peat moss.
It has been remarked, that occasionally the silt now occupying the former lake-bed, demonstrates the fact, that the under stratum was formed in great measure by decomposed vegetable matter, probably aqueous plants and the shed foliage of the encircling forest: the later deposit is considerably mixed with fine clay. The most probable solution of this problem is, that on the disappearance of the woods the exposed surface of the soil was washed down from the surrounding heights by every shower that fell, and if the land were tilled this denudation would be accelerated. Consequent upon the discharge of the water deepening and extending the outlet, and the contemporaneous deposition of matter held in solution in the lake-bed, small loughs in some instances now occupy sites which, from natural evidences, it is apparent must formerly have been extensive sheets of water; in other instances the large lake of ancient days, is now represented by several of diminutive size, connected by marshes that had at one time formed part of a great whole. In ancient times, however, the lakes most frequently appear to have gradually increased in height: this was due to the silting up of the outlet, under any circumstance a long and tedious process; for though the aqueous growth on the bottom of the outlet would, during the summer, impede and catch the heavy particles washed down or held in solution by the current, yet in winter, when it decayed, most of the accumulated matter would be swept away, so that in a hundred years the increase in height of the outlet would be scarcely perceptible. What then must be the age of lake dwellings, where three and even four superincumbent floors testify to the necessity of providing against the ever-rising water level!
Lakes, marshes, and woods, have in all ages afforded shelter to the conquered, and have often enabled them to set the invader at defiance. Pliny describes the Caledonian forests as “Romanorum armis terminus.” A race inferior in numbers, in arms, or in physical development, would avail themselves of artificial or natural bulwarks to ward off the attacks of dreaded enemies, and water and woods have from the earliest times formed important factors in the art of defence.