these warm currents, flowing uninterruptedly through polar regions, that we would attribute the high winter temperature and uniform climate to which the fossil floras and faunas of Greenland bear testimony.

If these views be at all reasonable, it seems unnecessary to call to our aid hypothetical changes in the position of the earth's axis. It may be admitted, however, that the climate of the Arctic regions must have been from time to time more or less affected by those cosmical causes to which Croll has appealed. So long, however, as insular conditions prevailed, the changes induced by a great increase in the eccentricity of the earth's orbit would not necessarily be strongly marked. Dr. Nansen objects to Croll's well-known theory that "it cannot account for the recurrence of conditions so favourable as to explain the existence in Greenland of a climate comparable to what we now find in Tropical regions." No doubt it cannot, but, as we maintain, there is no good reason for supposing that tropical or sub-tropical climates ever characterised any area within the Arctic Circle. The remarkable association in Europe, during so recent a period as the Pleistocene, of southern and temperate species of plants and animals, ought to warn us against taking the present distribution of lifeforms as an exact type of the kind of distribution which characterised earlier ages. It is safe to say that were our present continental areas to become broken up into groups of larger and smaller islands, so as to allow of a much less impeded oceanic circulation, the resulting climatic conditions would offer the strongest contrast to the present. And as the lands of the globe were apparently in former times more insular than they are now, it is hazardous to compare the climates of the present with those of the past. It is reasonable to infer, from the occurrence in Greenland of fossil floras which find their nearest representatives in Southern Europe and North Africa, that the winters of the far north were formerly mild and clement. But we cannot conclude, from the same evidence, that the Arctic summers were ever as hot as those of our present warm-temperate and sub-tropical zones.

But if the recent expedition has thrown no new light on the disputed question as to the cause of the high temperature which formerly prevailed in Greenland, it is needless to say that it has added considerably to our knowledge of the present physical conditions of that country. The view held by many that Greenland must be wrapped in ice has been amply justified, and we can now no longer doubt that the inland ice covers the whole country from the 75th parallel southwards. A section of Greenland in the latitude at which it was crossed by Nansen and his comrades "gives an almost exact mathematical curve, approximating very closely to the arc of a circle described with a radius of about 6500 miles. The whole way across the surface coincides tolerably accurately with this arc, though it falls away somewhat abruptly at the coasts, and a little more abruptly on the east side than the west." Taking the observations of other Arctic travellers with his own, Nansen is led to the conclusion that "the surface of the inland ice forms part of a remarkably regular cylinder, the radius of which nevertheless varies not a little at different latitudes, increasing markedly from the south, and consequently making the arc of the surface flatter and flatter as it advances northwards." He points out

that this remarkable configuration must to a certain extent be independent of the form of the underlying land-surface, which, to judge from the character of the wild and mountainous coast-lands, probably resembles Norway in its general configuration-if, indeed, it be not a group of mountainous islands. The buried interior of Greenland must in fact be a region of high mountains and deep valleys, all of which have totally disappeared under the enveloping mer de glace. It is obvious, as Dr. Nansen remarks, that the minor irregularities of the land "have had no influence whatever upon the form of the upper surface of the ice-sheet." That form has simply been determined by the force of pressure the quasi-viscous mass attaining its maximum thickness towards the central line of the country, where resistance to the movement due to pressure must necessarily have been greatest. Thus although the larger features of the ice-drowned land may have had some influence in determining the position of the ice-shed, it is not by any means certain that this central line coincides with the dominant ridge or water-shed of the land itself. For, as Nansen reminds us, the ice-shed of the Scandinavian inland ice of glacial times certainly lay about 100 miles to the east of the main water-parting of Norway and Sweden. Similar facts, we may add, have been noticed in connection with the old ice-sheets of Scotland and Ireland.

The greatest elevation attained by the expedition was 9000 feet. How deeply buried the dominating parts of the land surface may be at that elevation one cannot tell. It is obvious, however, that the mer de glace must be very unequal in thickness. According to Dr. Nansen the average elevation of the valleys in the interior cannot much exceed 1000 or 2000 feet, so that the ice lying above such depressions must have a thickness of 5000 or 6000 feet. It cannot, of course, lie so deeply over the mountain ridges. The eroding power of such a glacier mass must be enormous, and Dr. Nansen does not doubt that the buried valleys of Greenland are being widened and deepened by the grinding of the great ice-streams that are ever advancing towards the sea.

The expedition met with no streams of surface-water on the inland ice; indeed, the amount of superficial melting in the interior was quite insignificant. And yet, as is well known, many considerable streams and rivers flow out from underneath the inland ice all the year round. It is obvious, therefore, that this water supply does not come from superficial sources, as, according to Dr. Nansen, it is usually supposed to do. But surely it has long been recognised that such rivers as the Mary Minturn must be derived from sub-glacial melting. And the various causes to which our author attributes this melting have already frequently been pointed out. Earth-heat-the influence of pressure in lowering the melting-point of ice-and the friction induced by the movement of the ice itself have all long ago been recognised as factors tending to produce the sub-glacial water-drainage of an ice-sheet.

Dr. Nansen's speculations on the origin of the "drumlins "kames" of formerly glaciated areas will interest geologists, but are not so novel as he supposes. His description of what are known as "drumlins" is not quite correct. These long lenticular banks cannot be

said to lie upon boulder-clay, but are merely a structural form of that accumulation. And it is hardly the case that geologists have "performed the most acrobatic feats" in trying to explain the origin of the banks in question. The usual explanation is that they have been formed underneath the ice as ground-moraine-the upper surface of which varies in configuration-being sometimes approximately even, as in broad mountain valleys; at other times ridged and corrugated, as in open lowlands. And these modifications of surface are supposed to have resulted from the varying movement and pressure of the overlying icesheet. The drumlins, in fact, would appear to be analogous to the banks that accumulate in the beds of rivers. Many drumlins, indeed, are composed partly of solid rock and partly of boulder-clay, which would seem to have accumulated in the lee of the projecting rock, much in the same way as gravel and sand gather behind any large boulder in a stream-course. Dr. Nansen, apparently, to some extent confounds drumlins with "kames" and "åsar," of which certainly many strange and conflicting explanations have been hazarded. These, however, differ essentially from drumlins, for they consist exclusively, or almost exclusively, of water-worn and more or less water-assorted materials. And the most generally accepted view of their origin is that they have accumulated in tunnels underneath an ice-sheet. This is practically the same view as Dr. Nansen's. He thinks that when an ice-sheet has its under surface furrowed by running water, the ground-moraine will tend to be pressed up into the river-channels. The water will, in this way,

be compelled to hollow out the roof of its tunnel to a greater degree, and as the stream continues to work upwards the moraine will follow it, so as to partially fill the tunnel and form a ridge along the back of which the sub-glacial stream will run. The material forming the upper portion of the ridge will thus come to be composed mainly of water-worn and stratified detritus, derived from the erosion of the ground-moraine. This is an ingenious suggestion which may be of good service in some cases, but it is certainly inapplicable to most kames and åsar. If it were a complete explanation we ought to find these ridges consisting of an upper water-assorted portion and a lower unmodified morainic portion (boulderclay). But this is not the case, for most kames consist entirely, from top to bottom, of water-assorted materials. They are found running across an even or gently undulating surface of boulder-clay, and sometimes they rest not on boulder-clay but solid rock.

Dr. Nansen considers another geological question which has given rise to much controversy, and is still far from being settled-namely, whether the oscillations of level which have left such conspicuous traces in northern regions are in any way connected with the appearance and disappearance of great ice-sheets. Can a big ice-sheet push down the earth's crust by its weight and does the crust rise again as the ice melts away? Could a thick ice-sheet exercise sufficient attraction upon the sea to cause it to rise upon the land, and thus explain the origin of some of the so-called raised beaches of this and other formerly glaciated lands? Can the weight of a great ice-sheet shift the earth's centre of gravity, and, if so, to what extent? Each of these questions has been

answered in the affirmative and the negative by controversialists, and, until the geological evidence has been completely sifted, each, doubtless, will continue to be alternately affirmed and denied. All that need be pointed out here is that some of the movements which occurred during the Pleistocene period were on much too large a scale to be explicable by any of the hypotheses referred to.

OBITUARY: 189 0.

BERGHAUS, HERMANN.-No name is better known to geographers than that of "Berghaus"-uncle and nephew-who have, each in his time, produced the most famous cartographical works of the century. The uncle, Dr. Heinrich Berghaus, who died in 1884, at the ripe age of eightyseven, was the author of the first great Physical Atlas, well known in this country as being the basis of Keith Johnston's. The nephew, Dr. Hermann Berghaus, who died at Gotha, 3d December 1890, may be said to have continued and completed the work of his uncle. The third son of the Evangelical preacher Johann Berghaus, he was born at Herford, in Westphalia, 16th November 1828. Most of his life was spent at Gotha, where in 1850 he entered the Geographical Institute of Justus Perthes, just four years before Petermann went there. In Gotha he led an active life of study and work, which has been prolific in producing many valuable and original maps. Among his first works may be mentioned the physical map in Stieler's Hand-Atlas and Stieler's Schul-Atlas, also many miscellaneous school atlases, maps, and physical wall-maps. In 1861 he produced his Karte des Oetzthales Gletschergebietes; in 1863 his well-known Chart of the World, which has gone through many editions; in 1875, Physikalische Wandkarte von Europa; in 1878, Karte der Alpen; in 1881, Physikalische Wandkarte von Afrika. These works, however, are of but minor importance compared with his last work, Berghaus Physikalischer Atlas. Planned and worked out with the assistance of all the leading scientific geographers in Germany, it is undoubtedly the greatest work on physical geography at the present day, and will prove a lasting monument to Hermann Berghaus, although he has not lived to see it completed.-J.G.B.

BURTON, SIR RICHARD F., K.C.M.G.-By the death of Sir Richard F. Burton England has lost one of her most daring and successful travellers and explorers, a scholar of rare literary and scientific acquirements, and a gifted writer. He died on the 20th of October at Trieste, where he had filled the office of British Consul since 1872. He was born in 1821 at Barham House in Hertfordshire, and was the son of Colonel Netterville Burton of the 36th Regiment. He is said to have inherited from both sides of his parentage the wilful disposition and the love of unfettered action which were predominant elements in his character, and which had a great influence in the shaping of his destiny. In his early years he was left very much to his own devices. His education also was of the most desultory nature, and but little calculated to train him to habits of subordination. The most part, in fact, of his boyhood and youth

he spent on the Continent with his father, whose nomadic propensities never allowed him to settle for long in one place. To young Burton, however, this wandering life had its own advantages. He had keen powers of observation, and much was given him to observe. He had also a marvellous faculty for the acquisition of languages, and for the exercise of this faculty his changes of residence from country to country gave him the best of opportunities. His family returned to England in 1840, and he was then sent to Oxford. But, before completing his terms, he was dismissed from that seat of learning for contumacious disregard of its rules of discipline. During his residence, however, he had applied himself so zealously to the study of Arabic that before leaving he had mastered that difficult language. From the university he returned to his friends in London, who procured for him a commission in the East India Company's Service. He landed at Bombay towards the end of 1842, and thence proceeded to Baroda to join the regiment to which he had been posted as ensign. Here he displeased his superior officers by such eccentricities of conduct as had cut short his academic career. He was nevertheless promoted to the office of regimental interpreter, for which his accurate knowledge of Arabic, Persian, and Hindustani fully qualified him. He served in the brilliant campaign of 1843, in which Sir Charles Napier crushed the power of the Mohammedan rulers of Sind. The war over, he made excursions to explore some of the less-known parts of India.

In 1852 he first established his reputation as a most daring explorer by his journey to Mecca and Medina, which he undertook in the disguise of an Afghan pilgrim. Few records of travel are fuller of absorbing interest than the narrative in which he describes his perilous adventures on this pseudo-pilgrimage. His next expedition was to Somál-land, and in this he was accompanied by Lieutenant Speke. Here he made another pilgrimage scarcely less hazardous than the former; for, disguising himself as an Arab, he made his way alone to the sacred city of Harar, which, though known at one time to the Portuguese by name, had never been visited by a European. We find him next serving in the Crimean war, in the capacity of chief of the staff to General Beatson.

In his next expedition, which he made in 1857, in association again with Speke and under the auspices of the Royal Geographical Society, he crowned his fame by the discovery of Lake Tanganyika, rumours of the existence of which had been brought to the Coast by Arab traders and by missionaries. The success of this important undertaking was due mainly to Burton, whose familiarity with the Arab dialects enabled him to obtain from the Arab traders he encountered on the way a knowledge of the proper route for reaching the lake. The travellers, after many trials and sufferings, reached Ujiji in the middle of February 1858, about eight months after they had started from Bagamoyo. In the course of the expedition Speke, who had to leave Burton invalided at Kagé, reached the shores of the Victoria Nyanza, which he considered at the time, and afterwards practically proved, to belong to the Nile system. Burton took a different view, and hence arose a controversy between the two