METAMORPHIC STUDIES 
C. K. LEITH ann W. J. MEAD 
University of Wisconsin 
INTRODUCTION 
The early study of rock metamorphism consisted principally in 
the aggregation of a vast mass of more or less unrelated observations 
on rock alterations. Much of the literature on metamorphism 
has been so technical and so purely descriptive that it is natural 
that the general reader tends to postpone serious consideration of 
the subject. In recent years notable attempts by Van Hise," 
Grubenmann,’ and others have been made toward systematizing 
the subject and making it more available. Their works, especially 
that of Van Hise, are epoch-making and must necessarily be in the 
hands of the student of metamorphism. Later study has been 
more along quantitative lines and has resulted, as would be expected, 
in clarifying some of the principles, and in a better understanding 
of their significance. There seems to be need now of a more 
elementary treatment of metamorphism, shorn of some of the less 
essential details, and including recent quantitative developments 
which would be more widely used were their significance under- 
stood. This series of articles is an attempt to meet this need. 
Quantitative results, usually expressed graphically, will be used as 
a basis for the development of the principles of metamorphism. 
In the first article the general significance of the metamorphic 
cycle is discussed, as preliminary to a more detailed consideration 
of metamorphism. 
THE METAMORPHIC CYCLE DESCRIBED? 
The keynote of rock alterations is adaptation to environment. 
A molten rock or magma enters the outer shell of the earth and 
tC. R. Van Hise, A Treatise on Metamor phism, Mono. 47, U.S. Geological Survey, 
1903, pp. 1286. 
2Dr. U. Grubenmann, Die kristallinen Schiefer, Part I, 1904; Part II, 1907. 
Berlin. 
3C. K. Leith, “The Metamorphic Cycle,” Journal of Geology, XV (1907), 303-13. 
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