1916. J The Third Indian Science Congress. lxxxi 



will tell you the lessons I have learnt ; I do not, however, ask 

 you to believe that the problems are solved, for although I 

 may be led to place certain geographical and geodetic conclu- 

 sions before you, I realize that no solution will be satisfactory, 

 unless it proves acceptable to geologists, physicists and mathe- 

 maticians. 



You may think it peculiar that I should be speaking about 

 mountains at a place where only flat plains are to be seen, but 

 I may remind you that to the north of these plains stand the 

 greatest mountains of the Earth, and one of the most interest- 

 ing of the problems under consideration is, what is the rela- 

 tionship of these plains to those mountains. 



This is an outline map of the United Provinces ; you will 

 see that these Provinces have three geographical divisions; 

 there is the Himalayan area to the north, there are the level 



plains in the centre, and there is the ancient table-land on the 

 south. 



These great plains in the centre have been formed of loose 

 sediment brought down by the Ganges, Gogra and other rivers : 

 a borehole was sunk at Lucknow 1,500 feet deep, but no rock 

 bottom was reached. 



This is a section across the United Provinces. If you 

 compare the rocky area lying to the south of the plains with 

 that lying to the north, you will find on the south a massive 

 table-land ; the geologists have shown that this table-land 

 belongs to a very remote past. The mountains on the north 

 are totally different; here the rocks have undergone continued 

 compression, elevation, and disturbance throughout the ter- 

 tiary period, and our earthquakes prove that these movements 

 of the Earth's crust in the north of the United Provinces have 

 not yet ceased. 



I ask you to consider how does this ancient table-land join 

 on to these younger mountains that are always suffering from 

 movements in the crust ? If we could dig out from the Gan- 

 getic trough all the silt deposited by the Himalayan rivers, 

 what kind of rocky junction should we find under Lucknow ? 



The Contraction Theory. 



A hundred years ago the accepted idea was that mountain 

 ranges were due to the upward pressure of liquid lava and that 

 their elevation had been caused by volcanic forces. But when 

 geologists began to study the structure of rocks, they found 

 that mountains had suffered from great horizontal compres- 

 sion which was evident from the folding of strata. This dis- 

 covery led to the idea that mountains had been elevated not by 

 vertical forces, but by horizontal forces which squeezed the 

 rock upward. The wrinkling of the Earth's crust into moun- 

 tains by 'horizontal forces was explained by the cooling of the 



