164 TEOCEEBIKGS OF THE GEOLOGICAL SOCIETY. [Jail. 27, 



These features naturally divide the country into the district above 

 the escarpment, called the Deccan, and that below it, called the 

 Concan. The escarpment itself is known as the Syadree Range or 

 Western Ghauts. 



The Ghauts, therefore, are a vast escarpment and not a regular 

 mountain-range. Upon this escarpment, however, there occur moun- 

 tains of from 4000 to 5000 feet high ; and connected with it there 

 are several long and lofty hill-ranges, passing from it eastwards and 

 declining as they recede. 



The escarpment, generally precipitous, contains several special 

 precipices of from 1000 to 2000 feet in height, the crests of which 

 are at least as far advanced as their bases, and in a few very re- 

 markable cases, as at Hurreechunder, actually overhang them. 



For many miles north and south of Bombay, and for many miles 

 inland, the rocks of the district are, with limited exceptions, of igneous 

 origin, and varieties of trap. 



It is not the object of this paper to explain the general geology of 

 this district ; but it may be observed that there is evidence to show 

 that a line or band of volcanic vents extends north and south up 

 the axis of the Concan, whence most of the trap of Western India 

 appears to have been poured out, — eastward, at a moderate slope to 

 form the Deccan ; westward, at a much steeper inclination, into the 

 sea. There are also appearances connected with these vents which 

 seem to explain the great and sudden difference of altitude between 

 the country above and that below the Ghauts, as well as the singular 

 fact that tbe Ghauts themselves do not appear to have been pro- 

 duced by, or to be in any way connected with, any line of upheaving, 

 or of fault, or with any similar disruption or displacement, local or 

 general. 



The dykes under consideration are no doubt mineralogically in- 

 teresting ; but they are far more so from their connexion with the 

 various vents in the great volcanic band, and because they form a 

 part in the chain of evidence upon which the theory of the forma- 

 tion of this very remarkable part of India must rest. 



The dykes by which this part of the Concan is traversed vary in 

 breadth from one and two to ten, twenty, forty, and occasionally 100 

 or 150 feet, and are often many miles in length. They are most 

 numerous about the centre of the Concan. They are also numerous 

 in the great valley or bay known as the Malseje Ghaut. They are 

 seen, though less frequent, beneath the Nana, Copolee, and Beema- 

 Sunker Ghauts, and in the road between Panwell and the Bhore 

 Ghaut. Many occur upon the Ghauts themselves, and a few above 

 them upon the high tableland of the Deccan. They have also been, 

 traced in the islands of Bombay and Salsette. 



The contents of a few of these island dykes, and of one or two 

 upon the shores of the Concan, are altogether peculiar ; but with 

 these rare exceptions the dykes present very many points of resem- 

 blance. They are basaltic ; all have a tendency to the prismatic 

 form, which now and then, as at Gorabunder, in Salsette, and at 

 Callian, becomes columnar. The axes of the prisms are always at 



