Chap. XII.] soils and superficial deposits. 197 



The following is an analysis by Mr. Tween of a specimen of red soil 

 from Puttoocautaincooclicaud, a few miles South of Wodiarpolliam. 

 The specimen was taken from about 4 feet below the surface:— 

 Silica 64-3 ) jj^gQ^^^i^ie In acid. 



j.M8 { 'II \ 



» 1 



Peroxide of Iron 5-4 



Water and organic matter 7 



Hesidue, traces of Magnesia^ ! 0"82 



Lime, Alkali, Sulphuric Acid 



and Chlorine 



)>Soluble. 



100, 



00 J 



A specimen of shore sand from Cauverypatam, also analysed by 

 Mr. Tween, gave at least 75 '00 per cent, of silica, about 12 per cent, 

 of oxide of iron, and 8 of alumina; a little lime, manganese, magnesia 

 and soda being also present, with sulphur (in sulphuret of iron) and 

 chlorine. 



It appears from the above that the soil contains a smaller propor- 

 tion of silica than the sand of the sea coast, and more alumina or clay, 

 but the former was taken from a depth of 4 feet, and the sand from 

 the surface, where any argillaceous matter would have been washed 

 out by the waves. Had the sand been taken from 2 or 3 feet 

 below the surface, it would probably have contained a larger per- 

 centage of alumina judging from the muddiness of water penetrat- 

 ing at that depth when a hole is made in the sand. 



In the above analysis the percentage of iron is larger in the sand 

 than in the soil, but this varies considerably in other specimens of both, 

 as will be seen from the following estimations by Mr. Tween : — 



Iro?i. Fe^ O3 



Kich specimen of shore sand from Cauverypatam, 33*2 = 46 "6 



Average specimen same locality 8*8 = 12*5 



Specimen from Tranquebar 9"7 = 17*5 



Specimen from Negapatam 1*7 = 2*4 



