Note 19 — THE CHEMICAL RELATION OF IRON AND MANGANESE IN SEDIMENTARY ROCKS.
Reading edition
It has been suggested by A. A. Julien (Proceed. Amer. Assoc. Adv. Sci., Vol. XXVIII., 1879, p. 356) that in some cases the carbonates of iron and manganese may be only the fixed residue of organic compounds of more complex form once in solution in surface waters.