152 THE JOURNAL OF GEOLOGY. 
SiO, was to be expected. The very large amount of A1,O, is also 
very remarkable, it being the largest of the whole series; and, 
since calculation shows that the extra amount of AI,O, in No. 1, 
over No. 2, if determined as SiO,, would bring the percentage of 
the latter in No. 1 up to 58.46 (2. e., nearly equal to that of No. 
2), while the other oxides in the two are in closely similar amounts, 
it is feared that a mistake has been made by the analyst. On 
this account (though with some hesitation) I have decided not to 
use analysis No. 1 in the further discussion of these rocks. The 
mistake suspected does not, however, affect the other constit- 
uents and we find them quite normal, the alkalies low, with Na,O 
greater than K,O, and the lime, in accordance with the character 
of the plagioclase, higher than both together; while the iron 
oxides and magnesia present no special features of interest, except 
that the ferric oxide is much higher than the ferrous. 
In all the pyroxene-andesites (Nos. 3-7) the silica is low, 
though considerably higher in the last two, which are from 
Methana. Alumina inthe Mt. Kouragio rock (No. 5) is extremely 
low, but elsewhere quite normal. The iron oxides are greater in 
amount than in any other group, the ferric oxide being either less 
or only slightly greater than the ferrous, which is due to the 
abundance of hypersthene; in the hypersthene-free andesite of 
Mt. Chondos (No. 3) the ferric oxide is, on the contrary, much 
more abundant. They are all rich in lime and magnesia but poor 
in alkalies, the large amount of lime being due to the basic char- 
acter of the plagioclase. 
The acid dacites show a normal amount of Al,O,, but are 
much poorer in lime and richer in soda than the other groups 
which bears out the conclusions drawn from the optical exami- 
nation as to the character of the feldspar. The comparatively 
large amount of K,O in the Kakoperato dacite (No. 10) points 
to the presence of some orthoclase as has been already men- 
tioned. They are, on the whole, rather rich in iron and mag- 
nesia for the group, and in two cases the ferrous oxide is greater 
than the ferric. 
The segregations are all low in silica and alkalies but high in 
