ADIRONDACK BASIC INTRUSIVES B75 
It is the present purpose to state only the fundamental principles 
of this hypothesis, the reader being referred to Daly’s original 
papers’ for details. The essential points, according to Daly, are: 
1. “Each acid, batholithic magma has reached its present 
position in the earth’s crust largely through the successive engulf- 
ment of blocks broken out of the roof and walls of the batholith.”’ 
2. ‘The sunken blocks must be dissolved in the depths of the 
original fluid, magmatic body, with the formation of a ‘syntectic,’ 
secondary magma.” 
3. The period of most active intrusion, accompanied by stoping 
and abyssal assimilation, is when the magma is thoroughly molten. 
4. When the magma or stock becomes very viscous, the blocks 
(xenoliths) will neither sink nor become assimilated. 
In all of Daly’s papers it would seem that his hypothesis is 
generally meant to account for only large and more acidic intrusive 
bodies than the gabbro stocks here considered. However, there 
appears to be no reason why the essential principles of the hypothe- 
sis should not be applicable to these smaller and generally more 
basic stocks. 
It should be distinctly understood that the writer does not 
believe Daly’s hypothesis to involve the only processes to account 
for the type of occurrence and primary variations of these gabbro 
stocks, but rather the observed facts warrant his belief that mag- 
matic stoping and assimilation have been important processes. 
Other processes, such as marginal assimilation, or in the cases of 
certain smaller and more dike-like masses, simple pushing aside 
(displacement) of the country rock, may well enough have 
operated. 
SIGNIFICANCE OF THE MODE OF OCCURRENCE 
We have shown that the gabbro stocks are of the plug-like or 
pipe-like form with practically vertical boundaries. Now, as 
Harker says? 
An intrusive working its way up through solid rocks by “overhead stoping” 
must if this action be sufficiently continued, acquire something of the vertical 
t Amer. Jour. Sci., XV (1903), 269-98; ibid., XVI (1903), 107-26; ibid., XXVI 
(1908), 17-50. 
2 Natural History of Igneous Rocks, p. 86. 
