Chap. VII.] physical changes now in proghess. 148 



the old dam^ a section is shown, in which the artificial alluvium is seen 

 to be underlaid by a grey soil with some kunkur and numerous dead 

 specimens of the existing- river shells, as Corhictda consobrina, Uiiio 

 Melania, Palnd'ma, AmpuUaria, &c. 



Below the bund this grey bed is overlaid by a very thin layer of 

 darkish soil a few inches thick. Underlying it is a greyish-white soil 

 abounding in masses of kunkur, and containing apparently no shells 

 whatever. 



Great dams like the annicuts over the Cauvery, Coleroon, Vellaur 

 and Punniar cannot but greatly affect the direction and degree of scour- 

 ing action exercised by these several rivers, even to the extent of o'reatly 

 modifying their channels in the lapse of several years. 



Of causes tending to change the surface of the country, we must 



not forget to mention earthquakes, by which the 

 Earthquakes. . pot 



neighbourhood oi balem has been from time to 



time shaken, although not sufficiently to produce the overthrow of any 



buildings. 



Two shocks were experienced by us; the first in January 1860 

 when at Macdonald^s Choultry, a few miles south-west of Salem. The 

 vibration was hardly perceptible, but the subterranean noise was very 

 ■strong, and strikingly like the rushing of a heavy cart on a hard road. 

 The sound came distinctly from the east, and died away in the west. 

 "We subsequently ascertained that the inhabitants of Salem and of the 

 Shevaroys had, at distances of 13 and 20 miles respectively, been dis- 

 turbed the very same evening by a smart and very perceptible earth- 

 quake shock. 



The second was felt at Careputty " Travellers^ Bungalow,-'^ 8 miles 

 east of Salem, in the forenoon of April 12th, 1861. There were two smart 

 explosive upward shocks, accompanied by a loud noise, like the report 

 of small cannon. The shocks shook the Bungalow sufficiently to make 

 the rafters of the roof crack very audibly. The noise, which was dis- 



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