Heroes of science

by P. Martin Duncan

In 1855 and the two following years Sir Charles and Lady Lyell travelled much on the continent, and always with a view of studying existing nature so as to comprehend the past. He was gratified by finding that most of the rising teachers in Germany were using his books as text books for their lectures, and that the doctrines of Hutton he had elaborated were so much appreciated. In Switzerland, Lyell interested himself more than ever about the great remains of former ice action on the rocks. He was at one time disposed to believe that certain masses of mud containing angular stones, derived from a distance, could have been produced by the sea, but not finding any remains of marine animals, or evidence of such action as the ice would produce in rounding and waterwearing stone, he began to examine the influence of glaciers in wearing rocks and carrying the rubbish down with them. He was of course aware that there had been an age of cold in Switzerland, corresponding to the glacial epoch of Europe to the north, and he was therefore prepared to find some proofs of the former great extension of glaciers beyond their present limits. He was disposed to believe that the Alps were higher than they now are in that age of cold. In order to account for the former action of ice and the production of huge moraines, in comparison with which those now found at the glacier foot are pigmies, Lyell wrote: “In the glacial period, when the weight of ice was enormously greater, when in the region of the Alps there was so little melting, when glaciers at present only ten, fifteen, and twenty miles long, and from three hundred to one thousand feet deep, were fifty to one hundred, and even one hundred and fifty miles long, and four thousand feet deep (and if there is any truth at all in the generally received theory of the old Swiss glaciers, such must have been their gigantic dimensions), one may readily grant that the pressure and friction were so much in excess of what we now see as to explain the contrast between the ice work done in the olden times, and that accomplished in our own days, to say nothing of the probably disproportionate length of the periods compared.” He noticed an old terminal moraine, in advance of the new one of the Rhone glacier, covered with wild plants, some in full flower, and cut through in two places by the river; its height was only fifteen feet, and its width ninety feet. He went underneath the Viesch glacier in the Upper Vallais, and beyond it; in consequence of its having melted much, he saw a rounded and domed surface of granite, smooth, and with straight furrows a quarter of an inch deep exactly in the direction of the onward movement of the glacier. On the Ruffelhorn, on the right lateral moraine, that is on the surface of the ice close to the rocks, he saw a splendid mass of granite, angular in shape, and measuring fifty-nine feet long, forty-nine feet wide, and forty-two feet high. Its sides were polished and furrowed. This huge mass was being carried slowly down, by the glacier, and will be deposited at its foot some day or other. Once it formed a part of the valley side, and it fell on to the glacier, whose flanks had scrubbed it for many a long day. He particularly noticed how the glaciers had been advancing of late years (just as they are now receding).

Lyell followed out these researches on the south of the Alps, and he first of all made many excursions, accompanied by Gastaldi, one of the best of the scientific men of Turin, and by Michelotti, in order to compare the shells which are found fossil in the middle tertiary strata on the south of the Alps, with those of the molasse of Switzerland to the north. He found that these strata, separated by the great mass of the mountains, resembled each other somewhat mineralogically as well as in their fossils, but he was not able to make out that they were exactly of the same geological age, although it was highly probable. He wrote on the glaciers ancient and modern of the southern slopes of the Alps, and in relation to the former—“A comparison also of the extinct glaciers of the Italian and Swiss sides of the Alps can better be made from Turin than from any other place. Before my arrival I had seen, on the banks of the Lago Maggiore, some good examples of erratics and of moraines which had come from the Simplon, but these, as you might suppose, a priori are far inferior to those which have descended from the Val d’Aosta, or which belong to the mighty glacier derived from the combined snows of the Mont Blanc and the Mont Rosa group of Alpine heights. This glacier, although perhaps of less gigantic dimensions than that of the Rhone, has certainly left, as Gastaldi first pointed out in a memoir on the subject, a far more imposing monument of itself on the plains of the Po, than have the extinct glaciers of the Rhone or the Rhine, in the lower country of Switzerland.” He noticed that “J. D. Forbes has well shown in his book on the Alps, that a glacier is a peculiarly sensitive instrument for measuring the average of heat and cold, and that every slight difference of temperature causes it to increase or lessen in height and length.” And pursuing the argument, remarks that as geologists had shown from the nature of the fossil remains in lately formed gravels, that arctic animals lived far south in Europe, shortly before the existing state of things, we ought to find evidences of the cold climate which allowed those animals to live so far south. These evidences are at hand in the remains of the glaciers, which in those days extended far lower than they do now, and were grander in extent. Thus a lofty mound or ridge, two thousand feet high, called the Serra, running into the great alluvial flat of the River Po, where maize and mulberries grow, is a huge terminal moraine of an ancient glacier. Ice reigned supreme there in the glacial period, and brought down the stone from the distant hills, and deposited it on the Serra. In Forfarshire, Lyell had noticed the peculiar contorted appearance of the beds of clay, gravel and sand of glacial formation, and also in the mud cliffs of Norfolk. He was anxious to know whether any of the ancient glacial heaps or moraines of the country south of the Alps, showed similar indications of pressure and forcing along by ice. “It happened that a railway was making from Turin to Ivrea, and although they cut through the lowest part of the terminal moraines near Mazzi they have thought it worth while to make a tunnel, through which we walked.” Near the entrance, “I was delighted,” wrote Lyell, “to see that curious folding of the strata, which will cause the same beds to be here pierced by a perpendicular shaft, yet without the beds having participated in the movement.” Full of this important subject he wrote fully on it.

“In order to appreciate the distinctive character of this colossal moraine, you must reflect on the uniformity and evenness of the vast plain of the Po all round it, for, although really inclined from the Alps, it looks as level as the sea; then fancy the great mounds sloping up at angles of 20° and 30° to heights of 500, 1000, 1500 and 2000 feet; then consider that at the very extremity, as near Caluso, there are blocks of protogine which have come one hundred miles from Mont Blanc; also that the whole assemblage of stones is not like that which has issued from the Susa, or from any other valley, but confined to rocks such as now strictly belong to the basin of the Dora Baltea; also that the pebbles and fragments of stone, if of serpentine or any easily striable rock, are all striated, at least nineteen-twentieths of the whole, whereas in a recent glacier which has only travelled ten miles, you might only find one in twenty of the same stone striated; and lastly, think of the narrow vomitory which has disgorged this enormous quantity of material, the ravine above Ivrea being as obviously the source of the whole, as is the crater of Vesuvius the point from which its lavas have issued. When Gastaldi read his paper to the Geological Society at Paris, written jointly by him and Martens, Elie de Beaumont, who had many years before visited the ground, objected entirely to their conclusion that it was a moraine, but I never saw a stronger or more satisfactory case. But in the same paper the authors hazarded an opinion that although the old Alpine moraines stopped short after going a few leagues from the Alps, yet at some former time erratics had been conveyed to the summit of the Collina, just as “Pierre à Bot” and other blocks had been carried by the old Rhone glacier to the flanks of the Jura. Now when I read this at Zurich, I immediately recollected that in the valley of the Bormida, when I passed from Savona to Alessandria in 1828, I had been astonished at some very huge erratics of serpentine in the Miocene. Having never seen blocks of such enormous dimensions in any tertiary formation, I was relieved in 1828 at finding, in some spots on the Bormida, projecting fragments of serpentine in places which the erosion of the valleys had exposed to view. I concluded that they may not have travelled far, and when I saw some large blocks on the Superga (in 1828), I immediately suspected that as that hill consisted of beds of the same formation, the blocks might have been washed out of the Miocene not far off. I therefore now suggested this view to Gastaldi, and found that he was by no means tenacious of his printed theory, although he said that the blocks were many of them angular, of very great size, and accompanied by Alpine loam. We then examined the beds of the Superga, both those dipping to the north-west, and those to the south-east, and on both sides of this anticlinal are strata containing fragments of stone of various kinds, some not known in the neighbouring Alps or Apennines, from two to eight feet in diameter. On our ascent to the Superga I saw a thickness of sixty feet regularly stratified of this conglomerate, in which were fragments consisting chiefly of serpentine, but some of limestone, others of protogine granite, and one of the latter angular and eight feet in diameter. In less than half an hour’s search, I found two of the serpentine and one of the limestone pebbles with scratches, which would be called glacial if they were found in a modern moraine, though not such as you would select for examples for a museum. Still I searched this year in some recent moraines quite as long without finding better. As to the age of the beds, there is no doubt of their belonging to the Lower Miocene, the marine fossils of which we collected in strata both below and above them. These enormous blocks, therefore, were brought into their present position by causes which acted in the Miocene age. I know of no agency but that of ice which could have quietly let them down upon subjacent beds of undisturbed fine marl and sand. Hence I conclude that there was floating ice in the Lower Miocene period, and if the few scratches I saw really imply glacial striation, the ice-rafts were probably derived from glaciers which came down from mountains bordering the glacial sea; perhaps from the Alps, for that chain must have existed before the origin of a large part of the Lower Miocene. I have kept the specimens I found of these Miocene striated stones to show Ramsay, who will be interested in hearing, that in spite of some Brazilian genera of trees and insects, and not a few palms, and some reptiles of good size, and many other fossil genera found on both sides of the Alps and supposed to imply a subtropical climate, I am not afraid to appeal to ice as the only known cause capable of stratifying these great masses in the manner in which they occur.”

The evidence of former changes in climate was thus strongly impressed on Lyell’s mind, and the astonishing truth began to be strongly impressed upon geologists by him, that not only has the area of Europe witnessed ages of tropical heat, but also ages of considerable winter’s cold, and that there has been more than one glacial period.

Lyell visited Vesuvius and Etna in 1858, and how carefully he noticed every detail of the mountain structure, and how little he cared about “roughing it” may be gleaned from extracts from his diary sent to his wife:—

“Etna, Casa Inglese, Sept. 21, 1858.—Got off with two guides and two muleteers and four mules, at half past seven, in bright sunshine, from Nicolosi, and after a beautiful sunny ride of three hours through wooded craters, protected from the heat by my umbrella, was gradually enveloped in clouds. I saw a lava stream where the oaks had been surrounded by lava, which had taken the form both of upright and prostrate trunks, surrounding them with tuff, and the wood being burned up they are now cylinders of scoriaceous lava. After a couple of hours we got above the clouds, when about eight thousand feet high, but not till my hands were numbed, for I could not believe for a long time in the necessity of my putting on a cloak. After reaching this place, I set out with Angelo for the top of Etna, leaving Guiseppe to cook. We had now and then a drifting cloud, but on the whole splendid sunshine. I saw the spot at the foot of the great line where the Catanians quarried ice from under a current of lava. My guide saw the same thing some six years ago, while the eruption of 1852 was in progress, in August and September: the sand and lava ten feet thick, and four feet of ice below, and bottom not seen. Not far above the ice I warmed my hands at a fumarole where the steam and some sulphuretted hydrogen were given off at such a heat that I was obliged to be careful how I put my fingers in. This welcome heat enabled me to write. When we reached the edge of the crater the whole of Sicily was hidden except the higher part of Etna, between us and Montagunoli. But Lipari and Stromboli stood out in the sea very conspicuously. I made a rough sketch of the two craters; the smaller one has lately, I believe, fallen, and shows a section of some of the horizontal beds of lava, with which it had been filled nearly to the top. It was a considerable exertion climbing and going half round it after a seven hours’ ride, and this makes the Casa Inglese, which is the roughest place I was ever in, seem a hospitable mansion, as it saves our returning. The wind is whistling round and somewhat through it, but Dr. Guiseppe, I hear, has made it weather tight. There is no chimney and we have charcoal burners, but if the wind always blows like this I am not, at any rate, guaranteed from asphyxia.”

He got a list of one hundred and fifty shells of the newer pliocene clay on which Etna rests. Nine-tenths of them he found were of species belonging to the present floor of the Mediterranean Sea, and this, to his delight, confirmed what he wrote, and what has already been alluded to, regarding this deposit on a former occasion. At Bronte, Lyell saw the place where a crowd assembled in 1842, to see the lava flow into a great artificial reservoir of water. The torrent of melted stone came forward with a front of more than thirty feet high, and falling suddenly into the water, produced for a while no effect whatever, as if, as in the white hot metal in Butigny’s experiment, it required to cool down before it could cause explosion. At length it went off suddenly, and everybody but one or two out of fifty or more in number was killed.

During the years of his journeys in America and Europe, Lyell had paid special attention to the changes which were occurring on the surface of the earth amongst the rocks and hills, valleys, rivers, and sea-shores. He had dealt with inanimate nature largely. About the year 1859 he began to consider the changes which have occurred in the living things of the past, and to direct his attention to the subject of the antiquity of man and to the possible origin of species. He wrote to a friend in his usual half-jesting manner: “I have been much occupied with another geological subject besides that which your niece, Ellen Twisleton, irreverently calls the proving her to be first cousin to a turnip (a violet she should have said); I mean the antiquity of man as implied by the flint hatchets of Amiens, undoubtedly contemporaneous with the mammoth, and also the human skeletons of certain caves near Liège, which I believe to be of corresponding age. I regard the pyramids as things of yesterday in comparison of those relics.” Lyell struggled long in his mind against the theory of the great age of man on the earth, and converted himself to the belief in it, and in 1861 he wrote, after examining the associated remains of human art and extinct animals, such as the mammoth and hairy rhinoceros in England, that “the late discoveries at Herne Bay and Reculver convince me that man inhabited England when the Thames was a tributary of the Rhine.” He published a work on the antiquity of man, and then began to interest himself about the great age when ice reigned supreme over much of the northern hemisphere. Writing to his nephew he states: “On a hill called Moel Tryfaen (in North Wales), at a height of thirteen hundred feet above the sea, I found twenty species of fossil shells, all of living species, in sand and gravel fifty feet thick. You would have known most of them familiarly.” Some of these shells were of kinds now living close by in the sea, but others of kinds now living within the arctic circle. “The shells show that Snowdon and all the highest hills which are in the neighbourhood of Moel Tryfaen were mere islands in the sea at a comparatively late period, or when these living molluscs were flourishing.”

The researches of Lyell and Dawson in Nova Scotia have been noticed, and it is interesting to know that they were rewarded by the discovery of an air-breathing mollusc, and of several small amphibians of the age of the coal period, in the hollow of a stump of a tree, which dated back to that very ancient time. After the death of his friend Murchison, although the effects of age and a life of hard study were not unfelt, Lyell followed with great care the researches of Dr. Hicks relating to the oldest rocks of England. Lyell was intensely interested at the discovery of highly organized invertebrate animals in sandstones and shales, which hitherto had only yielded some doubtful worm tracks and impressions of plants, and he recognized the truth that no evidences of the beginning of living things were presented to the geologist. The researches of Carpenter, Thomson, and Agassiz concerning the natural philosophy and natural history of the deep sea were gratefully acknowledged by Lyell, as most important contributions to science, and the author of this memoir has a lively remembrance of Sir Charles’s intense excitement when the news first came that the sea was very cold at great depths.

Years passed on, and honours came to the hard-working, truth-loving man. He was elected president of the British Association, and was made a baronet. His sight began to fail, and it was a constant anxiety to many who saw him about London, to witness his constant exposure to danger. Availing himself of an excellent secretary, he still corresponded largely, and attended scientific meetings. But the end was at hand, and he lost his well-loved wife and then his brother. Dying from the results of a fall, Lyell was buried in Westminster Abbey, as a representative man of science. He was a brilliant example of a man who sought out truth, and braved public opinion for its sake, and who enlightened the world, caring little for ease and luxury, and assisting every fellow-labourer in the great science of geology.