LHE SOLIDIFICATION OF ALLOYS AND MAGMAS 
JAMES ASTON 
University of Wisconsin 
In this consideration of possible analogies in the solidification of 
alloys and igneous rocks, the treatment will be from a knowledge 
‘gained in the study of alloys, and with a confessed ignorance of the 
subject from the viewpoint of the geologist. 
That the value of the views to be advanced is clearly recognized, 
and that their applicability extends beyond the limited sphere with 
which the writer is familiar, is well shown in the following extracts 
from the writings of Dr. George F. Becker,’ of the United States 
Geological Survey. He says, 
In a plan submitted to the director when the new physical laboratory of the 
survey was first contemplated, I laid special stress upon the study of isomorphism 
and eutexia. 
Also, 
It would appear that the relation between liquids must be reducible to very 
general groups. Liquids must be either miscible or immiscible, and miscible 
liquids must exhibit either isomorphic properties or eutectic ones. 
And again, 
The applicability of eutexia to rock-classification depends upon the fact that 
it makes the systematic discussion of magmatic mixtures possible. Inasmuch 
as the subject-matter of lithology consists of mixtures, their classification must 
be carried out in terms of definite or standard mixtures, while the only mixtures 
possessing appropriate distinguishing properties are the eutectics. Thus in deal- 
ing with magmas or other heteromorphous miscible liquids, the eutectics seem 
to afford not only the best but the only natural and rational standards of reference. 
With any eutectic as a basis, a series of magmas may be prepared, each differing 
from the eutectic by containing an excess of one or more constituents. 
Here, then, is the key to the whole discussion—the comparison of 
alloys and igneous rocks from the standpoint of isomorphism and 
eutexia, a standpoint which has its rational foundation on the laws 
«Day and Allen, Zsomorphism of the Feldspars (Publications of the Carnegie 
Institution). Introduction by Dr. George F. Becker. 
569 . 
