ADIRONDACK BASIC INTRUSIVES 163 
observed, such dike tongues are so rare.. As Harker says: ‘“‘Al- 
though most of the bodies of granite and other plutonic rocks which 
have been loosely described as bosses, and so rendered in ideal 
sections, are doubtless of laccolithic or other stratiform shape; 
some, not of the largest dimensions, appear to have a plug-like 
form, with more or less vertical boundaries.’”’ The North Creek 
bosses are certainly of this plug-like or pipe-like form as shown 
by the very character of their eroded cross-sections and also by the 
vertical contacts with the country rock. Among the many fine 
contacts which came under the writer’s observation, not a single 
exception to the rule of vertical or practically vertical contacts 
was noted. 
In most cases the long axes of the stocks lie parallel to the 
foliation of the inclosing rock, though there are some notable 
exceptions. It would therefore seem that the molten intrusives 
generally followed the lines of least resistance but, even in these 
cases, the broad ends of the stocks cut sharply across the foliation 
bands, sometimes for a distance of several hundred yards. Such a 
phenomenon is well exhibited at the south end of the large stock 
(see accompanying map) where a big quarry has been opened up 
along the contact. 
The gabbro stocks are not at all uniformly distributed over 
the area of the quadrangle, the largest number being confined to 
a nearly north-south belt with a width of from 3 to 5 miles and 
extending through the middle of the quadrangle. This belt 
roughly corresponds to the general strike of the foliation. A 
secondary belt, about 1 mile wide and 5 miles long near the middle 
eastern boundary of the sheet, contains a dozen small stocks. 
With a single small exception the whole western side of the quad- 
rangle is devoid of gabbro masses. In the northeastern portion 
a few stocks occur, but they may really belong to some other belt 
not yet mapped. Thus we see that the gabbro intrusions were 
limited to pretty well defined areas or belts. 
Among these gabbro stocks four types of occurrence are espe- 
cially noteworthy as follows: (1) the normal, dark, basic gabbro 
with diabasic texture, and usually homogeneous throughout; 
* Natural History of Igneous Rocks (1909), p. 86. 
