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Show Development of Petrology.! Accurate chemical analyses of kka and of the component mineral! of rocks have become Increaalngli m-pnrtnnt m-pnrtnnt In the modem davelnptmtiof petrology The discovery of nawjirk typee la cnntlnuully providing (tab material and demonstrating that ha older rock analyara no longer pica for the reipiliement of tho prk.nt day. In tills work a leading pari .as been taken by Amerlcnn chemlaiajnd particularly those of th lined Hlatea geological survey In thi 1st thirteen year four bulletins (hve been Issued, giving complete annfa nf nmnr Amerlcnn rocks, conductuin the laboratory at Washington I |