140 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, 1890. 



earth, the first result of their decomposition. As you go lower, this 

 pales through orange into yellow, and the rock, further disintegrated 

 by the mechanical action of the water filtering through the soil, as 

 well as decomposed by the chemical action of such salts as it brings 

 down with it in solution, is gradually loosened and broken up till 

 the vertical prismatic columns become spheroidal or oval nodules 

 consisting of friable layers of a yellowish earthy crust, which you 

 can peel off, like the coats of an onion, round a hard dark coloured 

 nucleus, like the rock at the top. Lower still, even these lose then- 

 shape, and you find a mass of rotten brownish "moorum." 



Now, if you cross the island to the quarries on the east, you will 

 find the rock, as I have said, not so hard as that on the western 

 ridge, nor does it show the same columnar or prismatic structure. 

 These differences may have been caused by some difference in the 

 conditions under which the mass of molten lava cooled at the different 

 places. In other respects, the rock on the east generally resembles 

 that on the west, both mineralogically and in the manner of its 

 weathering into red earth, and finally decomposing through yellow 

 nodules into brownish moorum.* 



The rocky eminences of our island, then, would seem to have been 

 originally formed by outpourings of volcanic lava, and their shape 

 to have been determined by the force and direction of the flow. 

 But these rocky eminences we have already succeeded in connecting 

 with the main-land. You will, therefore, not be surprised to find, 

 on crossing the harbour, that the neighbouring bills of the Concan 

 are also of volcanic origin. 



But what is surprising is the immense area and depth covered h\ 

 the lava flows that produced them. As you go inland from the 

 coast, as you mount the western ghauts, as you cross the plateau of 

 the Deccan, as you scale the heights of Mahableshwar, you find that 

 the country for miles round, on all sides of you, is one great mass of 

 volcanic rock, move than 6,000 feet thick, and covering an area of 

 about 200,000 square miles ! With the exception of that which 

 produced, the greal basalt plain of the Snake River in Western 



*But below this again, on the east side, in the excavations for the extension of 

 the Prince's Dock, at a level which has not been reached at the bottom of the qnarries 

 on the Wesl recurs massive rock; apparentlj identical with that at the top. 



