July 6, 191 6] 



NATURE 



393 



the same range; the rocks composing it have had 

 nothing to do with its elevation. The Western Ghats 

 have been elevated, after the Deccan lavas had become 

 solidified, into surface rocks. Their elevation took 

 piace in the Tertiary age. 



The Depth of the Gangetic Rift. 



In considering the depth of the Gangetic rift we 

 must appeal, first, to geodesy, and then to seismology. 

 Now geodesy tells us that the compensation of the 

 Himalaya {i.e. the root of the Himalaya) extends 

 downwards to a great depth. I regard the Gangetic 

 plains and the Himalayan range to be the two parts 

 of one whole ; I believe that they have originated 

 together, and if the depth of Himalayan compensation 

 extends down to 60 miles, then I think that the 

 Gangetic rift may extend down to that depth also. 



Now let us turn to seismology; seismologists are 

 able to form rough estimates of the depths of earth- 

 quakes. In the Dharmsala earthquake Middlemiss 

 estimated its depth to be between 12 and 40 hiiles. 

 Middlemiss's maximum value is not very different 

 from the geodetic value. 



It is an interesting question to consider whether a 

 fissure in rocks could extend downwards to a great 

 depth. From a place near the Indus in Kashmir it is 

 possible to see a continuous wall of. rock 4 miles in 

 height, on the flank of Nanga Parbat. Mount Everest 

 stands erect 5^ miles above sea-level ; its summit 

 stands firm and rigid 11 miles above the depths of the 

 Bay of Bengal. We have, therefore, evidence that the 

 materials of the crust are strong enough to admit of 

 the continued existence of great differences in altitude. 



But Mount Everest is standing in air, whereas a 

 crack in the subcrust becomes filled with rocks falling 

 in and with fluid rock magma from below ; and the 

 walls of the crack thus get a support that Mount 

 Everest does not possess. It seems to me quite pos- 

 sible that a crack such as I have described may have 

 extended down to a depth of 60 miles by successive 

 fractures at increasing depths, the opening being filled 

 by falling material. 



Internal Causes of Mountain Elevation. 



I have shown you how zones of subsidence in the 

 crust are bordered by mountains, and I have now to 

 discuss the relationship of subsidence to elevation, of 

 troughs to mountains. The Red Sea is a zone of frac- 

 ture, and it is bordered on each side by a zone of 

 elevation. But along the Bombay coast the zone of 

 subsidence is bordered only on the one side by a zone 

 of elevation. The subcrustal crack from Surat to 

 Cape Comorin has been accompanied by a vertical 

 uplift of the Ghats, and I suggest for your considera- 

 tion that the vertical force which elevated the Ghats 

 was the expansion of the underlying rock due to 

 physical or chemical change. 



Mr. Hayden informs me that the specific gravity of 

 the rock composing the Neilgherries varies from 2-67 

 to 303 — that is, 14 per cent. — and that the rock of the 

 Hazaribagh plateau varies from 2-5 to 31 — 24 per 

 cent. 



The Western Ghats app>ear to have risen about 

 4000 ft. Now we know that the Western Ghats are 

 largelv compensated by underlying deficiency of 

 density; if the compensation of the W^estern Ghats 

 extends downwards to a depth of 60 miles, then an 

 expansion of 2 per cent, would be more than sufficient 

 to account for the elevation of the Ghats. Mr. Hay- 

 den finds variations of 14 and of 24 per cent, in the 

 densities of surface rocks, and yet an expjansion of 

 only 2 per cent, would account for both the elevation 

 and the compensation of the Ghats. 



The heterogeneous rocks composing the earth's crust 

 are continually undergoing changes of structure, known 



NO. 2436, VOL. 97] 



to geologists as metamorphism. At a depth of 30 

 miles the temperature is sufficiently high to melt all, 

 known rocks ; but increase of pressure raises the melt- 

 ing point, and the increase of pressure underground 

 may be sufficiently great to counteract the effects ot 

 the increase of temperature. So that at a depth of 

 even 60 miles rocks may still be scJid and rigid, as 

 geodesy leads us to believe they are. 



The main ranges of the Himalaya are composed of 

 granite; this granite has protruded upwards from 

 below. I suggest that the protrusion of granite is due 

 to expansion of rocks in the subcrust. The great 

 Himalayan range is 5 miles high, and the compensa- 

 tion of this range — that is, its underlying deficiency of 

 density — is estimated to extend downwards to a_ depth 

 of perhaps 75 miles. An underground expansion of 

 7 per cent, would be sufficient to account for the 

 elevation of the Himalaya. 



Many of the faults which intersect the Himalaya 

 may, I think, be ascribed to the shearing which must 

 have ensued when certain areas of the crust were 

 forced vertically upwards by the metamorphism of 

 subcrustal rock. Many distortions of surface strata 

 may be ascribed to local variations in the vertical ex- 

 pansion of deep-seated rocks. 



The f)eculiar sinuous curve of the northern Tibetan 

 border, concave on the east, convex on the west, is re- 

 produced in the north of Persia, and again in the Car- 

 pathians. The Persian ranges all have a trend frorr 

 south-east to north-west, except that the Caspian 

 subsidence seems to have pushed rudely in from the 

 north and forced the northern range into a sinuous 

 curve. It is significant that at the point of the Cas- 

 pian push stands the peak of Demavend, the highest 

 point in all Persia. Elevation is the companion of 

 subsidence. 



The conclusions which I have ventured to submit to 

 this meeting may be summarised as follows :— 



(i) The fundamental cause of both elevation and 

 subsidence is the occurrence of a crack in the sub- 

 crust. 



(2) Mountains are compensated by underlying de- 

 ficiencies of matter. 



(3) Mountains have risen out of the crust from a 

 great depth, possibly 60 miles. 



(A Mountains owe their elevation mainly to the 

 vertical expansion of subjacent rock. 



I have now had the great privilege of placing cer- 

 tain problems before you. My endeavour has been 

 to point out to this congress, and especially to its 

 younger members, the manv scientific secrets that 

 are lying hidden under the plains of northern India. 



UNIVERSITY AND EDUCATIONAL 

 INTELUGENCE. 



Oxford.— No honorary degrees were conferred at 

 this year's Encaenia, but on June 29 Mr. Douglas W. 

 Freshfield received the honorary degree of D.C.L. 

 The Public Orator, in presenting Mr. Freshfield, laid 

 especial stress on his advocacy of the claims of geo- 

 graphy for full recognition among university studies. 

 He spoke also of Mr, Freshfield's eminence as a 

 mountaineer, of his personal devotion to the theory 

 and practice of geographical science, and of his 

 achievements as a man of letters. 



Sheffield. — In connection with the new department 

 of glass technology the University has instituted a 

 diploma in the subject. The course of study will 

 cover three years, but candidates who have spent at 

 least two years in the glass industry may be exempted 

 from attendance in the first year's course under 

 certain conditions. The last tvix> years' study will be 

 devoted almost entirely to the chemistry, physics, and 



