From an Easy Chair

by Sir E. Ray Lankester

This is a matter requiring further discussion. It is probable, I may say in anticipation, that whilst natural selection in the struggle for existence is only obscurely operative (except as to alcoholism and some diseases) in civilised man, yet what Mr. Darwin called sexual selection—the influence of preference in mating—has an important scope, and it may be that hereafter it will be of enormous importance in maintaining the quality of the race.

Meanwhile, it seems that the unregulated increase of the population, the indiscriminate, unquestioning protection of infant life and of adult life also—without selection or limitation—must lead to results which can only be described as general degeneration. How far such a conclusion is justified, and what are possible modifying or counteracting influences at work which may affect the future of mankind, are questions of surpassing interest. In any case, it is interesting to note that the cessation of selection is more complete, and the consequent degeneration of the race would, therefore, seem to be more probable in the higher propertied classes than in the bare-footed toilers, whose ranks are thinned by starvation and early death. One may well ask, “Is this really so?”

38. The Movement, Growth, and Dwindling of Glaciers

Last summer we were watching the gradual change of the brilliant sunlight on the snows of Mont Blanc as the shadows crept up the pine-covered sides of the valley of Chamonix. We noted how the highest peak—the true summit of Mont Blanc—remained almost white and brilliant when the somewhat lower and nearer Dome de Gouter (so often, when clouds are about, mistaken for the true summit by tourists) had assumed a marvellous shade of saffron-rose colour. The crevasses of the glaciers were marked by an unearthly pale-green tint and delicate purple hues of weird beauty were spreading over the evanescent forms of the great snow-field, when one of the hotel guests—a citizen of Geneva—said, “Ah, yes! Look at them whilst you may, and wonder at them, those glaciers of the Alps. They are but the remnants, the roots, as it were, of the vast glacier which once filled the whole of this vale of Chamonix and spread down into the valley of the Rhone, and ploughed out with the slow movement of its huge mass the deep rock basin of the Lake Leman. Every year they dwindle, as they have dwindled for ages past, and soon—perhaps not more than another 100 years hence—they will have disappeared utterly from human sight and knowledge.” I continued to gaze at the scene, and as the night fell and the distant details were lost to view I felt as though a venerable, but decrepit, friend had passed from my sight, never to return. I was rejoiced to see the glaciers still there when the morning sun showed forth their strange opaque white and faintly green masses on the mountain sides—stupendous outpourings, as it were, of whipped cream tinted with pistachio-nut.

But was it true, that lament of the Genevese savant? Undoubtedly the glaciers in many parts of the Alps have been shrinking for the last thirty years. It is longer than that since I first saw the glaciers of the Chamonix valley, and there is no doubt that they have shrunk up since then, leaving acres of boulders and bare polished rock where was the ice I formerly climbed. The glacier of Argentière, near the upper end of the valley, is a mile or more shorter than it was; the ice caves which we used to visit at the foot of the Mer de Glace have melted away, and the end of the glacier is now high up above a precipitous surface of polished rock far from the site of the little pavilion, with its gay flag and amiable guardian, who used to exhibit the marvellous ice cavern.

I find on looking into the matter that it is true that there has, during the latter half of the past century, been a great dwindling of the lower end or “snout,” a drawing back, as it were, not only of Swiss glaciers, but of glaciers in other parts of the world—as, for instance, in Alaska and in the Himalayas. But I cannot avoid a feeling of satisfaction in recording the opinion of geological authorities that, contrary to the assertion of the Swiss pessimist, there is not any ground for believing that the present noticeable shrinking is due to a continuous process by which the enormous glaciers of remote ages have been incessantly reduced until now they are but rootlets or stumps of the former masses, destined to evaporate completely under the continued remorseless operation of increasing temperature. On the contrary, it appears that, though there are not accurate records and measurements as to past centuries as there will be as to present and future years, yet there is abundant evidence that Alpine glaciers have grown longer in some centuries and retreated in others. The period of alternate extension and retraction has not been ascertained with accuracy, but by some geologists it is supposed to be about fifty years. The retraction or shrinking is not due to a continuous increase of the temperature of the earth’s atmosphere—or of this hemisphere—but to contending causes which operate alternately towards increase and towards decrease when one or two hundred years are considered. Such are the greater or less rainfall and snowfall over a very large area, and the formation and persistence of clouds, concerned with which are probably those varying quantities—the spots on the sun.

The simple proof that glaciers have extended and again retreated within historic times is furnished by the fact that in some parts of the Alpine range the retreat of a glacier has uncovered ancient miners’ excavations, which must have been worked when the glacier did not reach the spot excavated. Subsequently the glacier advanced, and now after some hundreds of years it has again retreated and exposed the ice-covered borings and workings. The tradition of a glacier-enclosed village in the Zermatt mountains, shut off from the world by the advance of glaciers, lost and mysterious, is evidence that such advance has been observed by the native population.

The natives who live near glaciers know that they advance and retreat, but the fact that the whole glacier is really a slowly flowing viscous mass—a sort of frozen but not immobile river—was only established by scientific observation in the last century. The frozen river is fed by the snow which falls on the higher mountain ridges, and is squeezed into the form of ice instead of snow powder by its own weight as it slips down the inclines, warmed by the unclouded sunshine. The big glaciers move much more rapidly (or perhaps one should say less slowly) in the middle than at the sides. The measurements which have been made differ in different glaciers and in different parts of the same glacier, and show smaller movement in winter than in summer. The advance of the sides is retarded, as in the case of an ordinary river of flowing water, by friction against the rocks, which enclose the glacier as its banks enclose a river. A good average case shows a flow downwards in summer of half a foot a day at the sides and a foot and a half in the middle. The distance below the snow-line to which the flowing glacier descends down a mountain gorge—before it melts away and becomes a river of liquid water—depends, as does the rate at which it moves, in the first place, on the temperature of the region and on the sharpness of the slope. A glacier will flow downwards (as will a lump of pitch) along a scarcely perceptible incline, but more slowly than down a steeper incline, and it will, consequently, get further down into the warm valley without altogether melting away when the slope is steep.

But apart from these considerations, the bigger and thicker (or deeper) the glacier, that is to say, the more snow which each year falls at its starting-place and goes to making it, the further down will it flow before melting away; and it is the heavy snowfall of many years ago or of a series of years long past which has to-day reached in the form of ice the lower end of the glacier. So, though the lower end of the glacier may melt more quickly if the valley has become hotter, yet the heavy snowfalls of fifty years ago may only now have reached the valley, and may quite counterbalance the melting action of the warmer summers. Or reverse conditions, namely, less snow and lower or unchanged temperature in the valley, may prevail.

The Government of India has lately established a definite survey and record of the movement of several Himalayan glaciers and of the variation in the distance to which their “snouts” descend into the valleys. Twelve glaciers were examined last year, and will be properly watched in future. The Yengutsa glacier has gained about two miles in length since Sir Martin Conway visited it in 1892; the great Hispar glacier has slightly retreated. The Hassanabad glacier three years ago increased its length by a rapid progress of the free “snout” of as much as six miles in three months, and is now no longer increasing or advancing! Many years ago it had reached its present position, and then retreated. The rock masses carried on the ice and left in great heaps at the point where the glacier melted away are known as terminal “moraines,” and often serve to show the position to which the snout of a glacier once extended—far below its present limit. A curious fact as to the increase and shrinkage of glaciers is that of two neighbouring glaciers, as in the case of the glacier Blanc and the glacier Noir in Dauphiné (France), one may be advancing whilst the other is in retreat. Further study and knowledge of the causes of these variations will throw important light on questions of general meteorology.