SHELLS CONSIST OF 



1 ORGANIC SUBSTANCES AND n CARBONATE OF LIME 



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NiTROCEN HYDROGEN OXYGEN SULPHUR 



writer 



yd-ro. Siii/D ha teofQjnmonui 



I ! \ SULPHURETTED HYDROGEN^ 



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Sidpluitcof Qjumorbiay 



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CARBONATE OF AM^M 



SULPHATE or LIME OR 



GYPSUM. 



