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As agriculturists you should be able to judge from the external 

 appearance of soils and sub-soils and with such rough 

 and ready test as is afforded by a little hydrochloric acid, 

 their general character and composition, and a knowledge 

 of the principal minerals and of the method of distinguish- 

 ing and testing them will help you to judge still better 

 whether a soil is rich or poor and whether it is capable of 

 much improvement by the utilization of local resources. You 

 have been told the value of trap-rocks in the formation of rich 

 soils. The presence of a large variety of rocks is also of great 

 value in forming rich soils. A valley or a plain situated near 

 a hill where shales, sandstones, limestones and felspathic 

 granite or gneiss occur in abundance must be rich in plant 

 food. The junction of two geological formations is always 

 rich. The alluvial deposits differ in character according to 

 the difference in the character of rocks composing the hills 

 from which they are derived. Usually, however, alluvial soils 

 abound in plant foods, especially the farther they are situated 

 away from mountains. The delta of the Ganges represents 

 washings of the finer particles of all the Bengal hills, and what 

 is of great importance, it is full of organic matter being the 

 receptacle of the drainage of a large and populous tract of 

 country and of hills abounding in forests. The combination 

 of minerals and organic matter is far greater in the lower part 

 of the basin of the Ganges than in the upper parts. But 

 where in the upper parts of the basin the soil is clearly 

 derived from felspathic granite or trap-rocks and limestones, 

 it is richer than alluvium. 



