At Killee and Breagho, near Enniskillen, the peat has once more been cut away, restoring some of these great stones to the light.  If we count the layers and measure the thickness of the peat, we can tell how many years are represented by its growth.  We can, therefore, tell that the great stone circle, which the first growth of peat found already there, must be at least as old, and may be indefinitely older.  By careful count it is found that one foot of black peat is made up of eight hundred layers; eight hundred summers and eight hundred winters went to the building of it.  One foot of black peat, therefore, will measure the time from before the founding of Rome or the First Olympiad to the beginning of our era.  Another foot will bring us to the crowning of Charlemagne.  Yet another, to the death of Shakespeare and Cervantes.  Since then, only a few inches have been added.  Here is a chronometer worthy of our great cromlechs and stone circles.

Some of these, as we saw, rest on the clay, with a sea of peat twelve feet deep around and above them.  Every foot of the peat stands for eight centuries.  Since the peat began to form, eight or ten thousand years have passed, and when that vast period began, the great monuments of stone were already there.  How long they had stood in their silence before our chronometer began to run we cannot even guess.

At Cavancarragh, on the shoulder of Toppid Mountain, some four miles from Enniskillen, there is one of these circles; a ring of huge stone boulders with equal spaces between stone and stone.  A four-fold avenue of great blocks stretches away from it along the shoulder of the hill, ending quite abruptly at the edge of a ravine, the steep channel of a torrent.  It looks as if the river, gradually undermining the hillside, had cut the avenue in halves, so that the ravine seems later in date than the stones.  But that we cannot be quite sure of.  This, however, we do certainly know:  that since the avenue of boulders and the circle of huge red stones were ranged in order, a covering of peat in some parts twelve feet thick has grown around and above them, hiding them at last altogether from the day.  In places the peat has been cut away again, leaving the stones once more open to the light, standing, as they always stood, on the surface of the clay.

Here again we get the same measurement.  At eight hundred annual layers to the foot, and with twelve feet of peat, we have nine thousand six hundred years,—­not for the age of the stone circles, but for that part of their age which we are able to measure.  For we know not how long they were there before the peat began to grow.  It may have been a few years; it may have been a period as great or even greater than the ten thousand years we are able to measure.