1G8 CONTRIBUTIONS TO THE GEOLOGY OF MAINE. [bull. 165. 
While the Maine rock has the characteristics of bostonites, it does 
not seem wise to enlarge the scope of the term, especially since its 
presence in petrographic nomenclature is of doubtful utility. The term 
quartz-trachyte is therefore used to denote the trachytic character of 
the rock under discussion and at the same time to indicate the high 
percentage of silica. 
QUARTZ-TRACHYTE OF TOWNSHIP 9, RANGE 3. 
The rock at this place is easily separated into blocks along the lines 
of fracture, which intersect one another at small angles. Examination 
of one of these small blocks shows a very dense yellowish-white mate- 
rial with a somewhat glistening surface. Within this felsitic ground- 
mass are many specks of quartz about the size of a pin head, and 
a few larger cavities which are filled with quartz and carbonates, 
forming creamy -white areas with sparkling grains. Quartz also 
fills the minute cracks that are visible, and so secure is the cement 
that the rock is more easily broken in other directions than along 
these reunited fractures. In weathering, a rusty-gray zone about 
one-half inch thick is formed in which the cavities are filled with a 
yellow powder. 
The minerals in a fresh specimen, as revealed by the microscope, 
are apatite, plagioclase, orthoclase, and quartz, together with musco- 
vite, siderite, limonite, and a little calcite. The quartz forms per- 
haps one-third of the section and occurs as cement, closing fractures 
and filling in the spaces in the groundmass. The grains are usually 
broken into rude rhombs, and contain, as inclusions, numerous long, 
slender needles of apatite, together with occasional liquid inclusions. 
The feldspars form slender laths and a few square sections and are con- 
fined to the groundmass. The striated pieces about equal the unstri- 
ated in number, and since sections cut parallel to h can not show albite 
twinning, there is probably an excess of plagioclase over orthoclase in 
the section. By averaging many extinction angles the plagioclase was 
determined as oligoclase albite. Microperthite intergrowths occur. 
Muscovite forms part of the alteration products, and shows the cleav- 
age and surface structure characteristic of micas, and also shows a very 
faint difference of absorption. The siderite and calcite are found in 
patches throughout the rock, while limonite forms the yellowish specks 
so prominent in the more weathered portions. 
The structure of the groundmass is trachytic, although somewhat 
more granular than the Quoggy Joe specimen; quartz also takes a 
more important place among the feldspar laths. 
ANDESITES. 
Generally speaking, the andesites of this region belong to well-recog- 
nized varieties widely distributed over the earth, and differ in no 
