ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 20 CENTS PER COPY 28-N 12-41 CONTENTS. [The letters prefixed to the titles are those used to designate the chapters for advance publication. The Page. E. Gypsum, by R. W. Stone (May 17, 1917). F. Salt, bromine, and calcium chloride, by R. W. Stone (Apr. 30, 1917). J. Phosphate rock, by R. W. Stone (May 1, 1917). K. Grinding and polishing materials, by F. J. Katz (May 17, 1917). N. Potash, by H. S. Gale (May 9, 1917).. O. Bauxite and aluminum, by J. M. Hill (May 28, 1917). P. Alaska's mineral supplies, by A. H. Brooks (June 28, 1917). 3 |