Dec. 1861] 



Geology of the NeUyherriet. 



2-5.3 



mass of syenite of the Xeilgherries carried upwards with it a large 

 body of water, that had a considerable influence in conveying cer- 

 tain existing features to the configuration of the Neilgherries, 

 which I shall presently consider. 



The motion of the ascending s)enite may have been oscillatory : 

 vast masses rose from the interior of the planet and almost as soon 

 descended ; in some instances the foundering of these masses took 

 place at their centres, and left basins and funnels. The better to 

 understand this, I request the reader to turn over an hour-glass, 

 and mark the descent of the sand in the shape of a funnel : he 

 will then see in the subsidence of the inside of the incoherent 

 mass, as the sand descends, a partial illustration of my meaning. 

 This oscillatory action did not cease in the syenite until the whole 

 moving mass was completely fixed, Much of the water poured 

 downwards through the funnels. Other volumes of it rolled off 

 the plateau into the ocean below, creating in their descent those 

 deep grooves in the mass, met with on every side of it, and of 

 which the Guzlutty, Segoor, and Coonoor Ghauts, form the most 

 conspicuous examples : their cliffs, many hundred feet in height, 

 and the general extent of these vast chasms, at once dismiss the 

 idea of their excavation being due to the erosive action of the in- 

 significant streams that flow along their bottoms. If a circular 

 piece of paper be drawn with rapidity upwards through a basin of 

 water, its sides will be bent and grooved downwards, affording an 

 illustration of the process by which the deep fissures in the sides 

 of the Xeilgherries were originally formed. 



The waters having subsided into the depths of the earth, below 

 the plateau, and into the sea surrounding it, left a mass of syenite, 

 which would have presented the appearance of numerous peaks 

 and ridges surrounding hollows and funnels : many of the former 

 may yet be seen, while the latter have been since filled up by in- 

 vasions of other rocks from below. 



Posterior to these events another series of rocks were erupted, 

 of a different character to the preceding, being granite chiefly 

 pegmatite, but rarely that composed of the three minerals, quartz? 

 felspar, and mica ; the felspar in some cases being compact, and 



