432 



NA TURE 



[September i, 1904 



In Norway it is omnipresent. In this respect Scandinavia 

 is a region apart ; the streams of the more southern ranges 

 are scanty compared with those of a region where the 

 snowfall of two-thirds of the year is discharged in a few 

 weeks. Greece stands at the opposite pole. By what seems 

 a strange perversity of Nature, its slender streams are apt 

 to disappear underground, to re-issue miles away in the 

 great fountains that gave rise to so many legends. Arcadia 

 is, for the most part, a dry upland, sadly wanting in the 

 two elements of pastoral scenery, shady groves, and running 

 brooks. 



The Alps are distinguished by their subalpine lakes — 



"Anne lacus tantps? te, Lari maxime, teque, 

 Fluctibus et frcmitu assurgens, Benace, 



■of \'irgil. But perhaps even more interesting to the student 

 are the lake basins that have been filled up, and thus suggest 

 how similar lakes may have vanished at the base of other 

 ranges. 



I know no more striking walk to anyone interested in 

 the past doings of glaciers than that along the ridge of the 

 mighty moraine of the old glacier of Val d'Aosta, which 

 sweeps out, a hill 500 feet high, known as "La Serra," 

 from the base of the Alps near Ivrea into the plain of 

 Piedmont. Enclosed in its folds still lies the Lago di 

 Viverone ; but the Dora has long ago cut a gap in the 

 rampart and drained the rest of the enclosed space, filling 

 it up with the fluvial deposit of centuries. 



It is, however, the tarns rather than the great lakes of 

 the .\lps which have been the chief subjects of scientific 

 •disputation. Their distribution is curious. They are found 

 in great quantity in the .'\lps and Pyrenees, hardly at all in 

 the Caucasus, and comparatively rarely in the part of the 

 Himalaya I am acquainted with. 



A large-scale map will show that where tarns are most 

 thickly dotted over the uplands the peaks rise to no great 

 heieht above the ridges that connect them. This would 

 seem to indicate that there has been comparatively little 

 subaerial denudation in these districts, and consequently « 

 less material has been brought down to fill the hollows. 

 Agam, it is in gneiss and granitic regions that we find tarns 

 most abundant — that is, where the harder and more compact 

 rocks make the work of streams in tapping the basins 

 more lengthy. The rarity of tarns in the highlands behind 

 Kangchenjunga, perhaps, calls for explanation. We came 

 upon many basins, but, whether formed by moraines or true 

 rockbasins, they had for the most part 'been filled up bv 

 alluvial deposits. ' 



In my opinion, the presence of tarns must be taken as 

 an mdication that the portion of the range where they are 

 found has until a comparatively recent date been under 

 snow or ice. The former theory, still held, was that the 

 ice scooped out their basins from the solid rock. I believe 

 that It simply kept scoured pre-e.\isting basins. The ice 

 removed and the surrounding slopes left bare, streams on 

 the one hand filled the basins with sediment, or, on the 

 other, tapped them by cutting clefts in their rims. This 

 theory meets, at any rate, all the facts I have observed, and 

 I may point out that the actual process of the destruction 

 of tarns by such action may be seen going on under our 

 eyes in many places, notably in the glens of the Adamello 

 group. Prof. Garwood has lately employed his holidays in 

 sounding many of the tarns of the St. Gotthard group, and 

 his results, I understand, tend to corroborate the conclusions 

 stated. 



_ I desire here to re-affirm my conviction that snow and 

 ice in the High Alps are conservative agents : that they 

 arrest the natural processes of subaerial denudation ; that 

 the scouring work done by a glacier is insignificant com- 

 pared with the hewing and hacking of frost and running 

 water on slopes exposed to the open sky without a roof of 

 n^v^ and glacier. 



The contrast between the work of these two agents was 

 forced upon me many years ago while looking at the ground 

 from which the Eiger Glacier had then recently retreated. 

 The rocks, it is true, had had their angles rubbed off by 

 the glacier, but through their midst, cut as bv a knife, was 

 the deep slit or gash made by the subglacial torrent. There 

 IS in the Alps a particular type of gorge, found at Rosenlaui, 

 at the Lower Grindelwald Glacier, at the Kirchet above 

 Meiringen, and also in the Caucasus, within the curves of 



NO. 181 8, VOL. 70] 



old terminal moraines. It is obviously due to the action 

 of the subglacial torrent, which cuts deeper and deeper 

 while the ice above protects the sides of the cutting from 

 the effects of the atmosphere. 



One more note I have to make about glaciers. It has 

 been stated that glaciers go on melting in winter. Water, 

 no doubt, flows from under some of them, but that is not 

 the same thing. The end of the Rosenlaui Glacier is dry 

 in January ; you can jump across the clear stream that flows 

 from the Lower Grindehvald glacier. That stream is not 

 meltings, but the issue of a spring which rises under the 

 glacier and does not freeze. There is another such stream 

 on the way to the Great Scheideck, which remains free 

 when frost has fettered all its neighbours. 



I should like to direct your attention before we leave 

 glaciers to the systematic efforts that are being made on 

 the Continent to extend our knowledge of their peculiarities. 

 The subject has a literature of its own, and two Societies 

 — one in France, one in other countries — have been consti- 

 tuted to promote and systematise further investigations, 

 especially witli regard to the secular and annual oscillations 

 of the ice. These were initiated by the English .Alpine Club 

 in 1893, while I was its president. Subsequently, through 

 the exertions of the late Marshall Hall, an enthusiast on 

 the subject, an International Commission of Glaciers was 

 founded, which has been presided over by Dr. Richter, M. 

 Forel, and others; and more recently a French Commission 

 has been created with the object of studying in detail the 

 glaciers of the French Alps. A number of excellent reports 

 have been published, embodying information from all parts 

 of the globe. There has been, and is, I regret to say, very 

 great difficulty in obtaining any methodical reports from 

 the British possessions oversea. The subject does not com- 

 mend itself to the departmental mind. Let us hope for 

 improvement : I signalise the need for it. Of course, it is 

 by no means always an easy matter to get the required 

 measurements of retreat or advance in the glacial snout, 

 when the glacier is situated in a remote and only casually 

 visited region. Still, with good-will more might be done 

 than has been. The periods of advance and retreat of 

 glaciers appear to correspond to a certain extent throughout 

 the globe. The middle of the last century was the culmin- 

 ation of the last great advance. The general estimate of 

 their duration appears to be half a century. The ice is now 

 retreating in the Alps, the Caucasus, and the Himalaya, 

 and I believe in North America. We live in a retrogressive 

 period. The minor oscillation of advance which a few years 

 ago gave hopes to those who, like myself, had as children 

 seen the glaciers of Grindelwald and Chamoni.x at their 

 greatest, has not been carried on. 



Attempts are made to connect the oscillations of glaciers 

 with periods of sun-spots. They are, of course, connected 

 with the rain or snow-fall in past seasons. But the difficulty 

 of working out the connection is obvious. 



The advance of the ice will not begin until the snows 

 falling in its upper basin have had time to descend as ice 

 and become its snout ; in each glacier this period will vary 

 according to its length, bulk, and steepness, and the longer 

 the glacier is, the slower its lower extremity will be to 

 respond. Deficiency in snowfall will take effect after the 

 same period. It will be necessary, therefore, to ascertain 

 (as has been done in a tragic manner on Mont Blanc by 

 the recovery in the lowest portion of the Glacier des Bossons 

 of the bodies of those lost in its highest snows) the time 

 each glacier takes to travel, and to apply this interval to 

 the date of the year with which the statistics of deposition 

 of moisture are to be compared. If the glacier shows any- 

 thing about weather and climate, it is past, not contem- 

 porary, weather it indicates. 



Another point in which the Asiatic ranges, and particu- 

 larly the Himalaya, differ from the Alps is in the frequency 

 of snow avalanches, earthfalls, and mud-slides. These are 

 caused by the greater deposition of snow and the more 

 sudden and violent alternations of heat and cold, which lead 

 to the splitting of the hanging ice and snows by the freezing 

 of the water in their pores. I have noticed at a bivouac 

 that the moment of greatest cold — about the rising of the 

 morning star — is often hailed by the reports of a volley of 

 avalanches. 



The botanist may find much to do in working out a 

 comparison of the flora of my four ranges. I am no 



