368 Proceedings of the Royal Society of Edinburgh. [Sess. 
disintegration brought about by purely chemical means. This disintegra- 
tion is accompanied, or preluded, by a disengagement of organic matter 
soluble in alkali. Now the most characteristic feature of glauconite 
under the microscope is its cellular or reticulated structure ; it consists 
of a yellowish-green birefringent material enclosed in a dark isotropic 
network. From these data it seems legitimate to conclude that granular 
glauconite is composed of elementary particles of pure glauconite held 
together by a framework of some substance which is wholly or largely 
organic. 
In point of quantity, the total organic matter in granular glauconite 
plays but a small part. Combustion-analysis of Albatross grains revealed 
the presence of 031 per cent, of carbon, which corresponds to about twice 
that amount of organic substance. No difficulty was experienced in 
isolating the organic matter from Albatross grains by dissolving away 
the glauconite with a dilute mixture of hydrochloric and hydrofluoric acids. 
The residue then takes the form of black flakes, which under high 
magnification have the appearance of very ragged non-fibrous tissue of 
a brown colour. It is only partially soluble in dilute alkali, giving an 
extract similar to the dark alkaline liquor obtained when granular 
glauconite is disintegrated ; that is, there are at least two kinds of organic 
substance present, soluble and insoluble, respectively, in alkali. Conversely, 
flocculent glauconite, though it no longer yields anything to alkali, still 
contains organic matter, as is observed when it is acted upon by concentrated 
sulphuric acid. 
From the dark-red alkaline solution referred to above, the organic solute 
is completely precipitated on acidification in brown flakes ; these, when 
dried, form a dark-brown powder, whicli on heating chars without in- 
tumescence and leaves a ferruginous ash. A specimen containing 9'2 per 
cent, of ash (mainly Fe 2 0 3 with a little silica) was subjected to combustion- 
analysis with the following results, calculated on ash-free material : — 
Carbon ..... 54‘85 per cent. 
Hydrogen . . 5*79 „ 
These figures indicate that in elementary composition the substance 
resembles that not very well-defined body, humic acid. The characteristic 
and quite distinct odours emitted by the alkaline solution before and after 
acidification are exactly like those emitted by alkali-soluble humus (from 
peat or lake-deposits) in similar circumstances. It is, indeed, difficult not 
to believe that the organic matter in glauconite is of the nature of humic 
acid, i.e. a product of the decay of vegetable matter. If this be really the 
