“SKETCH OF 4GINA AND METHANA. 25 
sort of ‘‘network”’ of the plagioclase, the meshes being of glass. 
This “net” usually forms a core of the same shape as the crystal 
with a narrow, clear, inclusion-free zone of plagioclase surround- 
ing it. In other cases there is a central core of clear feldspar, 
then a ‘‘network” zone, and finally an outer clear border. 
Belowsky observed similar inclusions in the feldspars of andesite 
from West Ecuador,’ and they are not infrequent elsewhere. 
Besides these glass inclusions some small clear hornblende 
crystals, magnetite grains and apatite needles are also to be seen 
as inclusions in the feldspar. 
One of these apatite inclusions which is of special interest 
consists of a slender prism with low pyramidal terminations, .025 
mm. long, from one side of which projects a smaller prism at an 
apparent angle of 47°. This must be regarded as a twin and 
identical with the apatite twin from North Carolina? described by 
me, with twinning plane s (1121) and the angle between the c 
axes of 68° 28’. The lesser angle in the present case is accounted 
for by the fact that the twin does not lie with the plane of its 
two axes parallel to that of the section, as is seen on the use of 
higher powers. This occurrence is interesting since it serves to 
confirm the view that the first described case was a true twin and 
that the plane s (1121) is a twinning plane of the species. 
The hornblende of these andesites, which occurs in well 
shaped, though often broken, crystals (the uncommon plane @ 
(100) being often largely developed) is noteworthy on account 
of its color. This is a light, rather bright, olive-green, the 
pleochroism being very strong ; ¢ dark olive-green,  olive-green, 
& pale yellowish green. This color is characteristic of the horn- 
blende of all this group, with the exception of one specimen from 
Mt. Chondos which seems to have undergone decomposition to 
some extent.. Here the hornblende is of a dark or brownish 
green color, and the very strong pleochroism is: ¢ dark orange- 
tREIss and STUBEL, Reisen in Sitid Amerika. Das Hochgebirge d. Rep. Ecuador 
I. Petrog. Untersuch. I. West Cordillers, Tuican bis Escaleras Berge von M. Below- 
sky, Berlin, 1892, p. 28. 
2 Am. Jour. Sci., XXIII., 1887, p. 504. Cf Dana: Mineralogy, 1892, p. 767. 
