The Forms of Water in Clouds and Rivers, Ice and Glaciers

by John Tyndall

370. The most famous of these rocks, called the Pierre à Bôt, measures 50 feet in length, 40 in height, and 20 in width. Multiplying these three numbers together, we obtain 40,000 cubic feet as the volume of the boulder.

371. But this is small compared with some of the rocks which constitute the freight of even recent glaciers. Let us visit another of them. We have already been to Stalden, where the valley divides into two branches, the right branch running to St. Nicholas and Zermatt, and the left one to Saas and the Monte Moro. Three hours above Saas we come upon the end of the Allelein glacier, not filling the main valley, but thrown athwart it so as to stop its drainage like a dam. Above this ice-dam we have the Mattmark Lake, and at the head of the lake a small inn well known to travellers over the Monte Moro.

372. Close to this inn is the greatest boulder that we have ever seen. It measures 240,000 cubic feet. Looking across the valley we notice a glacier with its present end half a mile from the boulder. The stone, I believe, is serpentine, and were you and I to explore the Schwartzberg glacier to its upper fastnesses, we should find among them the birthplace of this gigantic stone. Four-and-twenty years ago, when the glacier reached the place now occupied by the boulder, it landed there its mighty freight, and then retreated. There is a second ice-borne rock at hand which would be considered vast were it not dwarfed by the aspect of its huger neighbour.

373. Evidence of this kind might be multiplied to any extent. In fact, at this moment, distinguished men, like Professor Favre of Geneva, are determining from the distribution of the erratic blocks the extent of the ancient glaciers of Switzerland. It was, however, an engineer named Venetz that first brought these evidences to light, and announced to an incredulous world the vast extension of the ancient ice. M. Agassiz afterwards developed and wonderfully expanded the discovery. Perhaps the most interesting observation regarding ancient glaciers is that of Dr. Hooker, who, during a recent visit to Palestine, found the celebrated Cedars of Lebanon growing upon ancient moraines.

[§ 55.] Ancient Glaciers of England, Ireland, Scotland, and Wales.

374. At the time the ice attained this extraordinary development in the Alps, many other portions of Europe, where no glaciers now exist, were covered with them. In the Highlands of Scotland, among the mountains of England, Ireland, and Wales, the ancient glaciers have written their story as plainly as in the Alps themselves. I should like to wander with you through Borrodale in Cumberland, or through the valleys near Bethgellert in Wales. Under all the beauty of the present scenery we should discover the memorials of a time when the whole region was locked in the embrace of ice. Professor Ramsay is especially distinguished by his writings on the ancient glaciers of Wales.

375. We have made the acquaintance of the Reeks of Magillicuddy as the great condensers of Atlantic vapour. At the time now referred to, this moisture did not fall as soft and fructifying rain, but as snow, which formed the nutriment of great glaciers. A chain of lakes now constitutes the chief attraction of Killarney, the Lower, the Middle, and the Upper Lake. Let us suppose ourselves rowing towards the head of the Upper Lake with the Purple Mountain to our left. Remembering our travels in the Alps, you would infallibly call my attention to the planing of the rocks, and declare the action to be unmistakably that of glaciers. With our attention thus sharpened, we land at the head of the lake, and walk up the Black Valley to the base of Magillicuddy's Reeks. Your conclusion would be, that this valley tells a tale as wonderful as that of Hasli.

376. We reach our boat and row homewards along the Upper Lake. Its islands now possess a new interest for us. Some of them are bare, others are covered wholly or in part with luxuriant vegetation; but both the naked and clothed islands are glaciated. The weathering of ages has not altered their forms: there are the Cannon Rock, the Giant's Coffin, the Man of War, all sculptured as if the chisel had passed over them in our own lifetime. These lakes, now fringed with tender woodland beauty, were all occupied by the ancient ice. It has disappeared, and seeds from other regions have been wafted thither to sow the trees, the shrubs, the ferns, and the grasses which now beautify Killarney. Man himself, they say, has made his appearance in the world since that time of ice; but of the real period and manner of man's introduction little is professed to be known since, to make them square with science, new meanings have been found for the beautiful myths and stories of the Bible.

377. It is the nature and tendency of the human mind to look backward and forward; to endeavour to restore the past and predict the future. Thus endowed, from data patiently and painfully won, we recover in idea a state of things which existed thousands, it may be millions, of years before the history of the human race began.

[§ 56.] The Glacial Epoch.