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in the lower Vindhyan rocks. The greatest depth of the 

 Azoic system is 26,000 feet. The soils are somewhat better 

 than granitic soils, but mica schists which contain no felspar, 

 but only quartz and mica, are poor. Quite recently Apatite 

 has been discovered in the mica mines of Hazaribagh, 

 a fact which is of considerable agricultural importance. 



4th. Above the Vindhyan system which represents a 

 transition between the true metamorphic gneiss and the true 

 sedimentary rocks of the Lower Silurian system which are 

 marked with ripples, come the Paleozoic rocks. The Palaeozoic 

 period is characterised by the first appearance of life, though 

 the remains of very few animals have been discovered in 

 the older of these rocks. A few zoophytes and trilobites and 

 graptolites and some shells called Oldhamia are the fossil- 

 remains found in them. The greatest depth of the Lower 

 Silurian rocks, as these older rocks are called, is about 30,000 

 feet and of the Upper Silurians about 108,000 feet. The 

 Lower Silurian rocks consist of shales, sandstones, lime- 

 stones, and conglomerates. This system is scarcely re- 

 presented in India. Lower Silurian beds are found overlying 

 the Himalayan gneiss. The Upper Silurian system consists 

 of the Old-red-sandstone ( 90,000 feet ), the Carboniferous 

 rocks (15,000 feet) and the Permian group, ( 3,000 feet) 

 or the New- red-sandstone. Of these the Carboniferous, 

 rocks are chiefly represented in India. These consist of 

 encrinitic limestones, shallow beds of sandstone, and coal 

 measures. The coal measures of Bengal are of great im- 

 portance, and coal in them being associated with iron and 

 limestone, their importance as centres of manufacture is 

 evident. Coal exists in an igneous or crystalline form 

 called graphite in the older metamorphic formations, and it 

 exists as coal in the later tertiary formations also, and 

 in the recent formations as peat. The coal of Bengal is 

 characterised by the usual fossils of the carboniferous systems 

 viz., lepidodendron and calamite. The Ranigunj coal fields 



