CH. XXXIX.

AGASSIZ.

411

struggle with life. His enthusiasm breathes out so naturally, and he speaks so regretfully of want of money, not for himself, but the work he longed to complete; while his gratitude is so sensible and heartfelt towards those who helped him to bring out these splendid additions to the science of zoology. His was a warm-hearted, earnest, and active nature, and he was beloved by all who knew him. It is pleasant to think that the Americans, among whom he spent the latter half of his life, from 1846 to 1874, appreciated him fully; so much so that Mr. Anderson, a rich tobacco merchant of New York, presented him in 1873 with the island of Penikese, one of the Elizabeth islands, north of New York, and with funds to establish there a marine naturalist's school. The last year of Agassiz's life was spent chiefly on this island, training up a group of young naturalists.

Agassiz proves that parts of northern Europe and North America must once have been covered with Great Fields of Ice, 1840.-It is, however, of the early part of Agassiz's life, while he was still in Switzerland, that we must now speak. Although his chief study was zoology, yet he could not live at Neuchatel, and travel about the Alps without being struck with those mighty rivers of ice, called glaciers, which creep slowly down the valley of the Alps in Switzerland, carrying with them stones and rubbish. (See Fig. 62, p. 412.)

These glaciers are formed by the snow, which collects on the tops of high mountains, and sliding down, becomes pressed more and more firmly together as it descends into the valleys, until it is moulded into solid ice, creeping slowly onwards between the mountains, and carrying with it sand, stones, and often huge pieces of rock which fall upon it. At last one end of this ice-river reaches a point where

the air is warm enough to melt it, and here it flows gradually away as water, leaving the stones and rubbish it has brought down lying in a confused heap, which is called a moraine.

Towards the end of the eighteenth century a famous geologist, named De Saussure, spent much time in examining

Glacier carrying down Stones and Rubbish (Lyell).

the glaciers of the Alps, and pointed out how they are now forming large deposits in the valleys, out of these heaps of rubbish which they bring down from the mountains. Since his time many geologists had taken up the study, but it was Professor Agassiz who first spelled out the wonderful history we can learn from it, about the former climate of our hemisphere. He noticed that rocks over which a glacier has

CH. XXXIX.

GLACIERS.

413

moved, are polished and grooved by the rough stones and sand frozen into the bottom of the ice, just in the same way as a piece of wood is scraped by the sharp iron at the bottom of a plane; and by these glacial scratches, or stria, as they are called, he could tell where glaciers had been, even though there was nothing else to show that ice had ever existed in the country.

Now, when he began to examine the slopes of the Alps many hundred feet above the present glaciers, and also in places where it is now too hot for ice to remain, he found to his surprise numbers of these glacial striæ and also remains of huge moraines, showing that the glaciers of olden time must once have been much larger and have stretched farther down the valley than they do now. And what was still more strange, these same marks were to be seen on the Jura Mountains, on the other side of Switzerland, where there are never any glaciers at present; moreover, on the Jura there were found huge blocks, some of them as big as cottages, which were not made of the same materials as the hills on which they rested, but were broken pieces of rock such as are now only found on the Alps.

It was clear, then, that these enormous pieces of stone must have been carried right across Switzerland from the Alps near Mont Blanc, and across the lake of Geneva, which is 1,000 feet deep, and then deposited on the Jura range near Neuchatel, where one block of Alpine gneiss, called the Pierre-à-Bot, as large as a good-sized cottage, sits perched on a mountain 600 feet above the top of the lake. How had these blocks travelled across the Swiss plains? No flood could have carried them, for they were too heavy, and besides they were not smooth as stones are which have been rolled in water, but were rough with sharp edges. Agassiz

was convinced, therefore, that they must have been carried by ice, and that huge glaciers must once have come down from the high Alps right across Switzerland, filling the lake of Geneva with ice, and carrying these blocks with them, as modern glaciers do now in the Swiss valleys.

This was a marvellous history, for it showed that all the lower land of Switzerland must once have been buried in ice, but other facts afterwards came to light which were more wonderful still. In 1840 Professor Agassiz came over to visit Great Britain, and when he went to Scotland with Dr. Buckland his practised eye discovered at once in the Highlands glacial scratchings, remains of moraines, and blocks which had been carried by ice; and soon it became evident that these were not confined to Scotland, for Dr. Buckland recognised them again in Wales and the North of England, where moraines and erratic blocks are to be seen in all parts of the country. So that here, too, in our little island, there must have been at one time huge glaciers as large as those now found in the Alps.

Nor was this all; for when once geologists knew where to look for these signs of glaciers, it began to be discovered little by little that parts of all the northern countries of Europe, Norway, Sweden, Russia, Germany, Switzerland, Northern Italy, England, and even on the other side of the Atlantic, Canada and North America, have been smoothed and scratched; and huge erratic (or wandering) blocks have been scattered over them, showing that in very remote ages (yet still while very nearly the same kinds of plants and animals as now were living upon the globe), the temperate parts of our northern hemisphere must have been intensely cold, causing a large part of these countries to be covered with great fields of ice, as Greer.land is in the present day.

CH. XXXIX.

BOUCHER DE PERTHES.

415

And just as we see now that icebergs break off from the Greenland glaciers, carrying with them stones and mud, and dropping them at the bottom of the sea; so in those times icebergs floated over many of the valleys of Europe, which were then submerged beneath the ocean. You may see in the railway-cuttings of Wales and in the sea-cliffs in the coast of Yorkshire and Norfolk huge masses of glacial drift, as it is called, made of mud and stones confusedly mixed together, which were dropped from icebergs travelling southwards from the ice-fields.

This period of cold is called by geologists the 'Glacial Period; and when you read works on geology you will see that it explains in a wonderful manner many curious facts in the later history of our earth, and the distribution of plants and animals upon it. For the present it is enough for you to remember that Agassiz first pointed out the signs of this cold period, and that this discovery was one of the earliest rewards of a patient study of causes which are going on now; for it is from the ice-action in Switzerland and Greenland in the present day, that we are able to understand how these huge ice-fields carried down erratic blocks and the mud of moraines during the Glacial Period.

Geological Proofs that Man lived upon the Earth in Ages long gone by, with Animals which are now extinct, 1847. -The second remarkable discovery which has been made in geology in this century is that of the antiquity of man; or the fact that man must have existed upon our earth long before the very earliest times of history or tradition; in an age when an elephant and a hyæna, of extinct species, roamed about England and France, together with some other strange animals which are not now to be found upon the globe.