Oct. 4, 1883] 



NATURE 



557 



Himalaya existed much in their present form during miocene 

 times and they may owe their excavation partly to the glacial 

 action of that period, when these mountain slopes rose from the 

 plain or margin of the ancient sea, far in front of the present 

 line of slope, and were far higher than now. This idea par- 

 ticularly strikes one when looking at the ice-ground spurs that 

 run out into the plain south of the Lago d'Orta. The general 

 and local elevation and depression that took place in post-miocene 

 times seem quite sufficient to account for the difference in the 

 comparative levels of adjacent transverse valleys, or an elevation 

 along the base of the chain, clearly indicated at Orta by the 

 northerly dip of the marine beds. It is reasonable to suppose 

 that these movements were exerted in different degrees, at points 

 Bg this face of the Alps and within the same, and that the 

 depression on the west has been less than on the east, so that the 

 --.ea never extended far up the valley of Susa, and to a compara- 

 tively sh nt distance up that of the Dora Baltea as compared 

 with Maggiore, and the formation and exces-ive depth of this 

 and similar lakes on the east is mainly due to this local depression 

 and elevation. Depression has steadily continued in the delta of 

 the Po as in the Ganges at Calcutta, for, at Venice, borings 

 showed depression of land surface to an extent of 403 feet, and 

 they did not reach the b.ise of the formation. 1 



It is not improbable that during the earlier extension of the 

 glaciers into the Maggiore basin,'-' the sea still had access to it ; 3 

 this would have greatly aided in the removal of the marine 

 deposits, and then the deeper erosion of its bed near the Borro- 

 mean Islands, so well put forward by Sir Andrew Ramsay. 

 When we see the gigantic >couring which glaciers have effected 

 in the hardest rocks on the sides and bottoois of valleys, when 

 we know for certain the enormous thickness they reached in the 

 Alps, I do not doubt for a moment their capability of deepening 

 a rock basin very considerably, or their power to move forward 

 over and against slopes so low as 2° to 3°. 4 



The earliest extreme extension of the glaciers was very great ; 

 we have evidence of it on the miocene hills near Turing their 

 surface being scattered over with transported material of ' great 

 size, quite unconnected with that other ancient period of gkcial 

 conditions during the miocene times mentioned above at a period 

 too remote to further dwell upon here. Even now I feel that in 

 dealing with this subject of the glaciation of the Alps, many of 

 you may say that I am departing too much from geography. 

 To this I would answer, glacial periods have been so intimately 

 connected with the interchange of sea and land conditions, that 

 where can the line be drawn in physical geography between the 

 past and the present? It is as undefined as the line which 

 separates species from genera. 



An enormous interval of time must have elapsed, during 

 which the cold was increasing and the glaciers advancing, and 

 during which the rivers were distributing the consequent waste 

 over the lower country, spreading out the more or less coarse 

 material, sands, and clays, in broad fans in front of all the gr at 

 gorges. Then came the first period of contraction of" the 

 glaciers, with many oscillations. Of this we have the evidence 

 in the moraines of Ivrea, Maggiore, &c. Sections of these 

 moraines show how they were piled the one up n the other ; 

 how the building up of one line of lateral moraine was followed' 

 by its partial destruction on another forward movement of the 

 ice, and the throwing down of another moraine upjn it. Then 

 were formed many of the smaller lakes, remains of which lie 

 amid the debris thrown out into the plain. The glaciers re- 

 tained this size for a very considerable time, and then apparently 

 very rapidly retreated to far within the mountains, but still for 

 another considerable period their dimensions were much larger 

 than those of the presen' tine, into which they seem to have 

 again rather rapidly shru k. 



Passing from the glacial action displayed in the outer Alps to 

 that in the Himalaya, we find ample evidence of a period of 

 great extension of such conditions, first in the erratics of the 

 Attock plain and the Potwar, 5 lying fifty to sixty miles from the 

 gorge of the Indus at Torbela. We have again the fact that in 



1 Lyell, Prin. vol. i. p, 426. 



-' With reference to the moraines of Ivrea, see pamphlet by I.ulgi Bruno 

 / tei rem costttnenti I anfiUatro alio sbocco delta Dora Batten. " 



3 The evidence is stronger as regards ihe Lrtgo Garda. 



* There appears to he too great an advocacy, on the one hand, of ice 

 action having done all the work of denud.,ti n ; while, on the other sime 

 writers consider this to have been extremely limited : it is the combination 

 of the two forces, I think, that effects so much and in so different a manner 

 and degree. 



, S ,. A . Verchere /. Asiat S. Bengal 1867. pp. ,, 3 ,, 4 ; Theobald, Record,' 

 0/ the Ideological Society of India, 1877, p. 140. 



Baltistan, in the Indus valley, glaciers have twice descended far 

 beyond their present limits, first down to Scardo itself, and then 

 to some thirty miles below their present limits ; while the 

 glaciers of Nanga Purbet, towering above the Indus some 22,000 

 feet, must have descended into the bed of that river. Even 

 allowing that the Potwar was not formerly a lacustrine basin, 

 the great debacles from the mountains would have been sufficient 

 to convey erratics fixed in ice to where they now lie. Cataclysms 

 of the present time, caused by glacial obstructions, have raised 

 the level of the Indus on the plain above Attock so much as eightv 

 feet. When these glaciers were more than double their present size, 

 gigantic floods must have often taken place, and formed boulder 

 deposits high above present levels : such high-level gravels are 

 to be seen not only in the Potwar, but also in the Naoshera 

 Dhun on the Rajaurie Tawi River, containing boulders of 

 nummulitic limestone and other rocks of the Pir Panjal on the 

 north. 



Again, north of the Chatadhar ridge, small glaciers, five to 

 six miles in length, at one time filled the lateral valleys, de- 

 scending towards the Cbenab River to about 5,000 feet ; and a 

 very perfect moraine occurs in one valley. This ground must be 

 very similar to that which has been described by Theobald as 

 occurring in the adjacent Kangra district ' on the flanks of the 

 Dhaoladhar ridge. Similar small glaciers existed, I believe, in 

 the valleys of the Kajna; range, but I think that neither in this 

 range nor in Budrawa did they ever descend into the main valleys ; 

 but the existence of these glaciers, together with the large snow- 

 beds, had much to do with the formation of the high-level gravel- 

 beds and fans through which the Jhelutn and Chenab have since 

 cut their way. 



In fact, examples of the former extension of glaciers are wide- 

 spread along the chain of the Himalayas from west to east. 

 True moraines, and moraine-mounds, at 16,000 feet on the north 

 side of the Baralasa Pass, attest the presence of glaciers on the 

 elevated plain of Rukshu, where now the snow-line is over 

 20,000 feet. 2 Drew gives much valuable information regarding 

 their former size. 3 On the east, in Sikkim, Sir Joseph Hooker 4 

 has described moraines of great height (700 feet) and extent. 5 

 Still further south and east, in the Naga Hills, a short period of 

 greater cold is indicated by the moraine detritus under the loftiest 

 portion of the Burrail range in latitude 25° 30'.° 



Whatever may have been the length of the glacial period in 

 the Alps — and it was very con-iderable — in the Himalayas it 

 cannot have been so long and so general, although to a certain 

 extent, contemporaneous. 



In the Alps glaciation meets the eye on every side, and the 

 mountains, up to a distinct level, owe their form and outline to 

 its great and universal extension. 



In the Himalayas it is difficult to trace polished surfaces or 

 stria; markings, even in the neighbourhojd of the largest glaciers 

 that are now advancing in full activity. It has been suggested 

 that obliteration is the result of more powerful denudating forces, 

 but the conditions are not so very dissimilar in the high Alps 

 and high Himalaya as to warrant this ; and wherever the oldest 

 stria; marks occur in the Himalaya, they are situated near the 

 bed of the valley. It may interest you if I give an illustration 

 or two of the size of these present glaciers as compared with 

 those of the Alps. The Baltoro glacier would extend, if placed 

 in the Toce valley, from the Simplon to the margin of the Lago 

 Maggiore ; or take another illustration of its length, from Mcnt 

 Blanc to Chatillon in the Valle d'Aosta. 



Although of -uch great length, these Himalayan glaciers could 

 never have reached the enormous thickness which the earlier 

 Alpine glaciers attained. This may thus be accounted for : in 

 the European area a generally low temperature prevailed down 

 to the sea level, while in the Himalayan it was local, and confined 

 to a higher level. It is evident that the snow-line has altered — 

 higher at one period, lower at another — down to recent times, 

 denoting changes of the mean annual temperature, which are not 

 yet fully understood, but have been attributed to very far distant 

 distribution or alterations of land, sea, and the oceau currents. 



Two periods of glacial extension are clearly defined, separated 

 by a milder interval of climate : during the earlier glacial period 



' Ibid. 1874, p. 86. 

 North of the Karakcram, in that now arid country, great moraines are 

 found in the valleys that descend into the Karakash, in the neighbourhood of 

 the Sujet pass, 17.600 feet. (Harold, Godwin-Austen in Epit.) 



3 The Jummoo and Kashmir Territories. 



4 II imalayan Journals, vol. i. p. 221. 



5 The equivalents, although very small, of such moraines are to be seen in 

 the Alps on the Simplon jutting out into the valley. 



6 Godwin-Austen, /. A. S. B. 1875, p. 209. 



