Xfl 



191(5., The Third Indian Science Congress. 



Here again you will see that one of the chains of the 

 Caucasus has foundered into the Caspian, and the western 

 extensions of the Caucasus have fallen into the Black Sea 

 ♦w *i, y £ re i, mountai n ranges collapsing ? May it not be 



t\Lt L T^ \°T * l8 CFackin S and the9e mountains are 

 railing into the rifts ? 



The Bombay Coast. 



I must now invite your attention to the Bombay Coast. 

 From the Tapti to Cape Comorin runs the range of mountains 

 known as the Western Ghats. This range is parallel to the 

 coast of India and about 40 miles inland ; it rises suddenly 

 with a steep scarp. The strata are almost as horizontal ^ 

 when first laid down ; they have never been compressed or 

 folded. 



The Survey has observed the plumb-line at different 

 points along this coast; it is always deflected strongly towards 

 the sea. To the west of Bombay and Mangalore there is the 

 deep sea; and to the east there is a massive range over 4,000 

 feet high : yet the plumb-line will hang seawards. If ' the 

 Western Ghats possessed the mass which they appear to 

 possess and which the Suess school ascribes to them, then the 

 Bombay plumb-line should be deflected 15 seconds towards 

 them. If on the other hand the Western Ghats are compen- 

 sated by deficiencies of mass underlying them in accordance 

 with the compensation theories of Pratt and Hayford, then the 

 plumb-line should hang vertically at Bombay. But the plumb- 

 lme takes neither of these courses: it hangs towards the sea. 

 We have been puzzled for years by the plumb-line at Bombay ; 

 we used to think that the rock under the ocean must be so 

 dense and heavy, that it was able to pull the plumb-lines 

 towards the sea. Major Cowie, however, observed in the 

 south of Kathiawar, and found that the plumb-line here had a 

 strong landward deflection. The seaward deflections occur 

 throughout the Bombay coast but not round Kathiawar. It is 

 only quite recently that we have realized we have here at 

 Bombay the same phenomenon as at Lucknow. 



In Northern India the plumb-line will persist in hanging 

 away from the visible mountains and at Bombay it takes the 

 same course, and when I consider its constant seaward deflec- 

 tion I can only suggest to you, that there must be, between 

 Bombay and the Western Ghats, a zone of subterranean defi- 

 ciency, a zone of fracture and subsidence like that of the 

 Gangetic plains. 



The secret is hidden below the Earth's crust: you will see 

 that the Ghats have been forced (possibly by underground 

 fracture) into a decided curve just above Bombay harbour ; it 

 is significant that at this curve the Deccan Trap rises to its 

 highest point, Kalsubai. 



