839 



as they bear witness to the powerful denuding agents at w^ork in 

 demolishing the mountains in this tropical island and illustrate how 

 far the rate of denudation depends on the geological condition. 

 Since, to my knowledge, the Indian geological literature does not 

 contain anything about these problems, I entered upon a study of 

 the available data in December last; the results have been brought 

 together in the accompanying table and will be discussed in detail 

 below. 



The available data were: 



1. Silt-contents, denoting the amount of matter held in suspen- 

 sion in the river water, estimated twice a day during a whole year. 

 A few times a month simuKaneous estimates were made of the silt 

 content of the surface water and the bottomwater. 



2. Discharge-estimates, corresponding with the preceding data, 

 indicating the amount of water, in cubic meters per second, carried 

 past the point of observation. 



3. Content of dissolved solid material in the riverwater, estimated 

 mostly only once every two months or less often. 



A combination of the data 1 and 2 shows the amount of silt per 

 second, day, month and year carried past the place of observation ; 

 that of 2 and 3 shows the amount of dissolved solid material, 

 transported from the riversystem per month and per annum, so that 

 apart from the material transferred to the sea along the bottom, 

 we get in this way a survey of all the materials carried away from 

 the riversystem in one year. Most of the observations being made 

 in the lower course, where no doul)t the bulk of the transported 

 material in suspension and in solution are discharged, we may 

 assume that the values found in this way, cannot be far below the 

 real amount of the transported matter. 



The total amount of the materials carried past the place of 

 observation — by weight — was reduced to cubic meters by 

 dividing by 2.5 — which was taken for the average specific gravity 

 of the transported stones — and then the average annual denuda- 

 tion was computed by apportioning the result over the system above 

 the place of observation. 



For some rivers the observations were no! made for a whole 

 year. In those cases we made interpolations. 



In view of the available niaterial it is not pretended that these 

 results are strictly accurate. Observations only twice a day, inter- 

 polations for some months, observations of the dissolved materials 

 only some times a year, the absence of data of the material trans- 



