Nov. 2, 1883.] 



♦ KNOWLEDGE ♦ 



271 



very great ; we have evidence of it on the miocene hills 

 near Turin, their surface being scattered over with trans- 

 ported material of great size, quite unconnected with that 

 other ancient period of glacial conditions during the miocene 

 times mentioned above at a period too remote to further 

 dwell upon here. 



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 conse- 

 quent waste over the lower country, spreading out the 

 more or less coarse material, sands and clays, in broad 

 fans in front of all the great gorges. Then came the first 

 period of contraction of the glaciers, with many oscilla- 

 tions. Of this we have the evidence in the moraines of 

 Ivrea, Maggiore, &c. Sections of these moraines show how 

 they are piled the one upon 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 upon it. 

 Then were formed many of the smaller lakes, remains of 

 which lie amid the dihri>: thrown out into the plain. 



The glaciers retained 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 present time, into which they seem to have again 

 rather rapidly shrunk. 



In the Himalayas 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 fiO to 60 miles 

 from the gorge of the Indus at Torbela. We have again 

 the fact that in Baltistan, in the Indus valley, glaciers 

 have twice descended far beyond their present limits, first 

 down to Scardo itself, and then to some 30 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. Cataclysms of the 

 present time, caused by glacial obstructions, have raised 

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

 as 80 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 Rajurie 

 Tawi River, containing.boulders of numraulitic limestone 

 and other rocks on the Pir Punjal 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 Chenab River to about 5,000 feet ; 

 and a very perfect moraine occurs in one valley. 



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 gla- 

 ciers on the elevated plain of Rukshu, where now the snow- 

 line is over 20,000 feet. 



Whatever may have been the length of the glacial period 

 in the Alps — and it was very considerable — in the Hima- 

 layas it cannot have been so long and so general, although, 

 to a certain extent, contemporaneous. In the Alps glacia- 

 tion 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 dillicult to 

 trace polished surfaces or striae markings, even in the 

 neighbourhood of the largest glaciers that are now advanc- 

 ing 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 nnd 

 high Himalayas as to warrant tliis ; and wherever the oldest 



striaj marks occur in the Himalayas, they are situated near 

 the bed of the valley. The Baltoro Glacier would extend, 

 if placed in the Toce valley, from the Simplon to the 

 margin of the Lago Maggiore ; or, to take another illustra- 

 tion of its length, from Mont Blanc to Chatillon in the 

 Valle d' Aosta. 



Although of such 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 tem- 

 perature 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 

 ocean currents. Two periods of glacial extension are 

 clearly defined, separated by a milder interval of climate ; 

 during the earlier glacial period the Indus valley was filled 

 with those extensive lacustrine and fluviatile deposits, 

 mixed with the large angular debris, such as we see at 

 Scardo, which may be coeval with the extreme extension of 

 the Alpine erratics so far as the miocene hills south of 

 Turin. The second period followed, after a long interval of 

 denudation of the same beds, and would correspond with 

 the last extension of the great moraines of Ivrea, Maggiore, 

 C'omo, Ac, followed V)y a final retreat to nearly present 

 smaller dimensions. 



Nowhere on the south face of the Himalayas do we find 

 valleys presenting any features similar to those of the 

 Southern Alps, particularly on the Italian lakes, which are 

 the result in the first place of marine denudation, suc- 

 ceeded by that of depression, and finally powerful ice-action. 

 On the south face of the Khasi and Jaintia Hills, however, 

 which are orographically connected with the peninsula of 

 India — the conditions altogether ditierent — we find long 

 stretches of water of considerable breadth and depth ex- 

 tending within the hills, and not unlike in miniature the 

 Italian lakes. These valleys, worn out of the sandstone 

 and limestone rock, have been formed here, to some extent 

 by the aid of marine action and the subsequent depression 

 along this line of hills, also marked here, as in the Western 

 Bhutan Doars, by the absence of beds newer than the 

 nummulitic. 



THE AMATEUR ELECTRICIAN. 



HATTERIES.— V. 

 " TJUZZLED " writes to say that he cannot understand 

 _L the theory which asserts that in the simple cell 

 (zinc and copper immersed in water) the hydrogen, freed 

 by the combination of the zinc with the o.xygen of the con- 

 tiguous water molecules, deprives the next molecules of 

 their hydrogen, and associates itsi If with their oxygen, and 

 that a series of such exchanges takes place until the copper 

 is reached. He wants to know why one molecule or pair 

 of atoms of hydrogen should break up a molecule of water 

 simply to replace the hydrogen originally pertaining to it 

 This is truly a ticklish problem to many. It has, I suppose, 

 puzzled more or less every one who has given any atten- 

 tion to the subject, to a greater or less extent. The theory 

 generally accepted is that hydrogen in its nascent condition 

 (that is, at the moment when it is freed from combination) 

 is more potent, that is more electro positive, than that 

 hydrogen which is already in a state of combination, and 

 that it is on this account able to displace it A rough 

 and perhaps a somewhat inconclusive method of demon- 

 stratiii'' that the hydrogen freed at the surface of the 



