i6 The American Geologist. .Ta""<"-y. 1901. 
section is exposed by the cutting of the railway which skirts 
the base of the mountain between Miletta and Eastman, in a 
direction normal to the axis of folding as well as to the strike 
of the adjacent sedimientary rocks. On the whole, however, 
any observations that can yet be made on the larger petro- 
graphical relations of the mountain must still be regarded as 
of a preliminary nature. 
The rocks of Orford mountain comprise two main divi- 
sions. The first, which is found on approaching the moun- 
tain from the eastern side, i. e., along the railway from Milet- 
ta station, and which is intrusive through Cambro-Silurian 
strata, constitutes much the greater part of the mountain 
and is an igneous rock of rather uniform character, probably 
the product of a single eruption 
Its extent along the railway track is as nearly as possible 
a mile and a half and it forms the only rock traversed in the 
ascent of the mountain by the usual paths from "Orford 
crossing." The second division comprises several rocks of 
different varieties both igneous and sedimentary folded to- 
gether in a comparatively narrow band running along the 
western base of the mountain. It is about one-third of a mile 
in width on the railway, and so far as known does not appear 
in the more elevated portions of the mountain at all. The 
actual contact between these two divisions of the mountain 
has not yet been found. 
The rock of the first, or greater, mass has a uniformly 
green coler, showing gray grains on a freshly broken surface. 
Quartz veins are very abund n* i". it and joint planes and 
seams are often studded with small quartz crytals. Yellow- 
ish-green patches, some times as much as a foot in diameter, 
are nnmcrons. They are harder than the normal rock and 
stand out in relief on the weathered surface, owing to the 
more resistant material of which they are composed ; of which 
the mineral epidote appears to be a prominent constituent. 
The texture of the rock becomes much finer towards the outer 
edge, and also towards the top of the mountain, where the 
cooling of the igneous mass would have taken place more 
rapidly and under less pressure. 
In thin sections examined by the aid of a microscope, 
the rock is found to have had its original characters much 
