40 THE JOURNAL OF GEOLOGY. 
less numerous, though larger, and arranged often in lines of flow. 
The groundmass is very compact, of a darker, bluish gray color 
and sub-greasy luster, containing some hornblende needles. The 
enclosures in this rock, which are very numerous and striking, will 
be described later. With this Kakoperato rock must be classed 
the rock near Agio Vesili on the west coast of A¢gina, on the 
ground of its general appearance, though no analysis of it was 
made and quartz grains are not nearly as abundant as in that just 
described. 
Under the microscope the slides of these occurrences show 
much the same features.!. The hyalopilitic groundmass is largely 
predominant, the glass base being colorless (with no perlitic 
cracks), and the microlites (which are largely feldspar) showing 
a beautiful flow structure, but being more abundant in the Kako- 
perato than in the Anzeiou specimens. Crystals of hornblende 
and plagioclase and grains of magnetite are also rarer in the 
groundmass of the former while abundant in the latter. Many of 
the microlites and lathes of feldspar in the Kakoperato dacite 
are untwinned and show parallel extinction which points to the 
presence of orthoclase, belief in which being strengthened by the 
comparatively large quantity of K,O shown on analysis. It is 
noteworthy that neither in these nor in any of the other dacites 
was quartz met with as a groundmass constituent. 
The phenocrysts are chiefly hornblende and plagioclase, only 
a few quartz sections being found in the slides. Magnetite is 
present, though not abundantly, in rather large, well shaped 
grains which must be classed rather with the phenocrystic than 
with the groundmass constituents. 
The hornblende which occurs only as phenocrysts is in small 
but well shaped crystals, often broken. In color they are 
brownish green (that of Agio Vesili is greenish brown) and quite 
fresh and unaltered. Rare inclusions of plagioclase, augite, and 
magnetite are found. In general character and habit they much 
resemble the hornblendes of the Stavro rock, though the color 
is more inclined to brown. 
™On the whole the slides much resemble those of the dacite from Lassen’s Peak in 
my possession. 
