360 Prof. Ehrenberg on the Microscopic Life 
not a hydrate, but anhydrous oxide of iron, and therefore quite 
distinct from the very similar iron-ochre, is favourable to this 
view. (Compare No.5.) Ten analyses have enabled 25 Phy- 
tolitharia, amongst which is 1 Spongolithe and 1 Polygastrian, 
to be determined as constituent elements. The small quantity 
of inorganic sand is not glassy, but strongly doubly refractive ; 
and the behaviour of its white particles resembles that of the 
white portion of the cinders indicated as oligoclase. The Li- 
thospheridia predominate, and are the smallest forms. Lithosty- 
lidium rude is large, and often very numerous. Although the 
Lithospheridia have their outlines always sharp and smooth, the 
Lithostylidia usually appear spongy and, as it were, eaten away. 
One of their chemical constituents appears to have been ex- 
tracted from them. The stelligerous forms, described as Li- 
thosemata, occur not unfrequently. 
7. Dark-brown earth under the turf of the most elevated sur- 
faces. No. 166.—The fine dark-brown earth, which becomes 
black when wetted, does not effervesce with acids, When cal- 
cined, it becomes first blackish, and then of a darker brown than 
before. It contains many root-fibres of plants, which are visible 
to the naked eye. When washed, there remains a fine variegated 
sand in which many Phytolitharia are imbedded. Lithospheridia 
are rare; but Amphidiscus truncatus, Lithostylidium clepsammi- 
dium, and L. rude are abundant. No Lithosemata. In all, ten 
analyses gave 4 Polygastria and 21 Phytolitharia, such as parti- 
cles of grasses, but no Spongolithe. ; 
8. Dark-brown earth under the turf of the highest region of the 
island. No.165.—Dull dark-brown-earth, which does not effer- 
vesce with acids, and, when calcined, becomes first black, and 
then white. Impalpable when rubbed between the fingers. In 
ten analyses, 24 organic forms were found; these were all sili- 
cious particles of grasses, except 1 Spongolithe, most probably 
blown in. 
In the form, abundance, and intermixture of the forms, this 
earth exactly resembles the red earths Nos. 5 and 6. Only a small 
quantity, disappearing in the mass, of decomposed vegetable 
cellular tissue (true humus) is intermixed with it ; but still this 
is the part which gives the brown colour. Iron, on the con- 
trary, is entirely wanting. This fact is important, because by it 
the iron in Nos. 5 and 6 is shown. to be a foreign intermixture, not 
appertaining to those grass-particles, and either produced by vol- 
canic action or by non-volcanic deposition from water. The 
apparently black humus of the island, where quite free from 
voleanic dust, is only formed by Phytolitharia with a little 
soluble cellular matter, and: without lime. 
