PREHISTORIC BOMBAY 135 



in the island of Salsette, and is thence continued, with similar 

 interruptions, northward along the coast, past Versova, Myr Island, 

 Dharavi, and Bassein, to Arnalla. 



This ridge on which you are standing then is part of a great sea wall 

 of solid rock, here some half mile thick through from east to west, 

 which protects some 35 miles of the western shores of India from 

 the encroachments of the sea. Here and there, we have seen, it has 

 itself suffered from the inroads of the waves. But how well it is 

 calculated to withstand their fury, even during the onslaught of the 

 S.-W. monsoon, to which it stands full exposed, you can see if you 

 examine the rocks around. As the quarry-men at work below will 

 tell you, they are so hard as to be incapable of " dressing," and 

 require the finest steel-pointed crowbars for the making of the holes 

 in which to put the blasting charges by which alone they can be 

 rent. 



Now, look again at the ridge on which you are standing. Through 

 its whole length, you see, it rises precipitously on the eastern side, 

 but slopes gradually to the west. The reason for this you will find 

 presently, when examining more attentively the strata exposed by 

 the operations of the quarry-men aforesaid. You will then see that 

 these strata are not laid quite horizontally, but are tilted at an angle 

 of some 15° from east to west. Yet they are all parallel to each other, 

 so that the tilting force must have been applied to all alike, after they 

 had been formed. This tilt, or " dip," as it is technically called by 

 geologists, by unequally exposing the strata on the declivity to the 

 action of the weather, has caused the gradual slope to the west. 

 But before proceeding to a closer investigation of the struc- 

 ture of our island, let us look over its surface from our post 

 of vantage. At our feet lies a flat expanse of low ground, some of it 

 evidently below 'the level of the sea outside, which is excluded by 

 the causeways at the Mahaluxmi Vellard, Worli, and Sion. It 

 si retches from the base of the western ridge on which we stand, 

 eastward, unbroken by any eminence, till it reaches the chain of 

 rocky hills that mark the eastern limit of the island at its northern 

 end. 



This level plain, between the two lines of raised rocky ground on 

 its west and east, is evidently of different formations ; for 



