^{page 364 note *} No less than 43 analyses are quoted by Leith, , U.S. Geol. Survey Mon., xliii, p. 239, 1903.Google Scholar Many of the specimens, however, are of continental origin, and some are not true glauconites at all.

^{page 364 note †} Proc. Roy. Soc. Edin., xxvi. p. 259, 1906.

^{page 365 note *} Murray, and Lee, , Mem. Mus. Comp. Zoöl., xxxviii, p. 40, 1909.Google Scholar These authorities express the opinion (p. 41) that the sample may have been subjected to washing during or after the dredging.

^{page 367 note *} The determination of ferrous iron, which, in presence of organic matter, is the mineralogical chemist's despair, was carried out with special precautions in the present analyses, as follows:—One or two gr. of material are placed in a large platinum crucible with 15 cc. of 20 per cent. sulphuric acid and about 1 cc. of strong hydrofluoric acid. The crucible is closed off by a leaden block having two leaden tubulures, through which a current of carbon dioxide is sent through the apparatus. After 15 minutes' gentle boiling, the glauconite is dissolved, and the crucible is allowed to cool in carbon dioxide. The contents are transferred to a measuring-flask, made up to 50 cc., and allowed to stand in an atmosphere of carbon dioxide for 5–6 hours, by which time the organic matter will have settled to the bottom. An aliquot portion of the clear liquor is then pipetted off and titrated with permanganate. Organic matter would seriously impair the accuracy of this determination only in so far as it went into solution in dilute acid at boiling temperature; in the case of glauconite there does not seem to be much danger from this source.

page 367 note † Clarke, (U.S. Geol. Survey Mon., xliii, p. 243, 1903 Google Scholar) arrives at the same formula, KSiFe₂O₆, from a consideration of the older analyses, but leaves water of hydration out of account on the ground that it is “zeolitic.” As a matter of fact, glauconite can take up several molecules of “zeolitic” water, but the one molecule which persists in the sharply dried mineral would rather seem to be water of constitution.

^{page 369 note *} Proc. Amer. Assoc., xxviii, p. 363, 1879.

^{page 369 note †} Challenger Reports, “Deep-Sea Deposits,” p. 389, 1891.

^{page 369 note ‡} Loc. cit., p. 254.

^{page 369 note §} Challenger Reports, “Deep-Sea Deposits,” p. 380; Murray and Lee, loc. cit., p. 20.

^{page 370 note *} Loc. cit., p. 263.

^{page 371 note *} Loc. cit., p. 243.

^{page 371 note †} Zeitschr. anorg. Chem., xiii. p. 231, 1897.

^{page 371 note ‡} Zeitschr. f. phys. Chem., xxvii, p. 323, 1898.

^{page 371 note §} Zeitschr. anorg. Chem., lxiii, p. 691, 1909.

^{page 372 note *} Analysis under No. 1 in Proc. Roy. Soc. Edin., xxx. p. 190, 1910.