November 2, 1883.] 



SCIENCE. 



595 



have survived the many geological changes, and 

 still inhabit the rivers and low grounds of India 

 to-day. The fresh-water shells are the same now 

 as then. Many species of antelope lived in the 

 neighboring plains and uplands. The elephant was 

 there in the zenith of its existence, for no less than 

 thirteen species have been found fossil in northern 

 India. 



If we now turn to Europe to compare formations 

 of similar age, Lombardy and the valley of the Po, 

 with the southern side of the Alps, present to us 

 somewhat similar physical features. A large area 

 of about the size of the north-west Punjab, once a 

 part of the miocene sea, is occupied by a remnant of 

 rocks of that age, considerably elevated and tilted, 

 but not to such an extent as those of the Himalayas. 

 Near Turin these dip towards the mountains; and a 

 very short examination shows the undoubted glacial 

 character of some of the beds; and, as the whole 

 formation is marine, their large sharply angular 

 material, much of which is Jurassic limestone, was 

 probably transported from the adjacent mountains 

 by the agency of ice in a narrow sea.J After the 

 great crushing and alteration of the previous out- 

 lines of the, whole country, another sea filled the 

 basin of the Po, and pliocene deposits were laid down 

 in a sinking area extending to the base of the moun- 

 tains all round the new bay or gulf. Re-elevation 

 again set in, and with it, or soon after it, the advent 

 of another and the last glacial period. 



Before the last great elevation of the alpine chain, 

 the whole line of seacoast. therefore, ran even high 

 up the long deep valleys of Maggiore, Como, Garda, 

 etc. Then came the gradual but uneven elevation 

 of the whole area, including the miocene hills south 

 of the Po; and lacustrine and estuary conditions 

 prevailed over much of the plain country. The 

 lapse of time was probably enormous ; and, as the land 

 rose and the sea retired, the climate gradually became 

 cooler, and ushered in the glacial period. With the 

 change and the increased volume of the mountain 

 torrents, the destruction of the upraised marine plio- 

 cene beds commenced, and finally culminated in the 

 extreme extension of the glaciers, even into the plains. 

 The denudation of tlis formation has been enormous 

 along the base of the Alps, and only mere remnants 

 are to be found. Their preservation is due to their 

 being in position where the great denuding force, 

 the ice, has been unable to touch them : in other in- 

 stances the early deposition of moraine matter upon 

 them has acted liked a shield, and prevented their 

 entire destruction. 



The scattered remnants of the pliocene formation 

 south of the Alps show well how soon a great for- 

 mation may be completely destroyed by denuding 

 forces. 



' Xo trace lias been observed of this glacial period in the 

 miocene of India. The moat lofty portions of the chain had not 

 then attained a greater elevation, probably, than 14,000 to 18,000 

 feet, and the outer axis-lincfl far less. However, In the tertiary 

 bed)« (middle eocene?') of the Indtis valley, below T.eh, such 

 conditions are indicated by I.ydekker (^.}femoira of geological 

 suTVfy of India, vol. xxii. p. 104, which 1 have received since this 

 address was sent to press). 



It is an established fact, that the great valleys of 

 the Alps and Himalaya existed much in their present 

 form during miocene times ; and they may owe 

 tlieir 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. 



It is not improbable, that, during the earlier exten- 

 sion of the glaciers into the Maggiore basin, the sea 

 still had access to it. This would have greatly aided 

 in the removal of the marine deposits, and then the 

 deeper erosion of its bed near the Borromean Islands, 

 so well put forward by Sir Andrew Ramsay. When 

 we see the gigantic scouring which glaciers have 

 effected in the hardest rocks on the sides and bottoms 

 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 

 b.tsin very considerably, or their power to move for- 

 ward over and against slopes so low ,as 2° to 3°.' 



Passing from the glacial action displayed in the 

 outer -\lps 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, lying fifty to sixty miles from the 

 gorge of the Indus at Torbela. We have again the 

 fact that in Ballistan, 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. 



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- 

 raounds, at 16,000 feet on the north side of the 

 Baralasa Pass, attest the presence of glaciers on the 

 elevated plain of Bukshu, where now the snow-line 

 is over 20,000 feet. Drew gives much valuable in- 

 formation regarding their former size. On the east, 

 in Sikkim, Sir Joseph Hooker has described moraines 

 of great height (700 feet) and extent. Still farther 

 south and east, in the N.aga Hills, a short period of 

 greater cold is indicated by the moraine detritus 

 under the loftiest portion of the Burrail range. In 

 latitude 2.5° 30'. 



^Yhatever may have been the length of the glacial 

 period in the Alps, — and it was very considerable, — 

 in the Himalayas it cannot have been so long and 

 so general, although to a certain extent contem- 

 poraneous. 



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

 and the mountain?, up to a distinct level, owe their 

 form and outline to its great and unlvcilsal extension. 

 In the Himalayas it is difficult to trace polished sur- 

 faces or striae markings, even i)i the neighborhood 

 of the largest glaciers that are now advancing in 



* There appears to be too great an advocacy, on the one hand, 

 of Ice.action having done all the work of denudation; while, on 

 the other, some writers consider this to have been ''Xtremely 

 limited. It is the combination of the two forces, I think, that 

 effects so much, and in so different a manner and degree. 



