360 CK LEIP AND We Jo MEAD 
dolomite in later as compared with earlier formations seems to be a 
pretty well-established fact. If it is true, it supports our inference 
of the progressive accumulation of limestone near the earth’s 
surface. 
5. Alumina and silica the carriers—We are beginning to think 
of the cycle as one which is traveled through principally by alumina 
and silica; that these substances act as buckets which carry out 
toward the surface the bases in different relative proportions. The 
lime and soda are not carried back to a large extent. The potassa 
and magnesia are carried back to a larger extent. Iron, so far as 
we know, is carried pretty well through. Water and carbon 
dioxide in katamorphism are the effective agents in breaking up 
the combinations of the alumina and silica and thereby unloading 
the buckets. In the anamorphic phase of the cycle, the water goes 
down in the otherwise empty buckets in combination with alumina 
and silica as clay, but only for a short distance, because the hydrates 
are not adapted to the conditions of pressure below. Alumina and 
silica are not only redistributing substances, but by their combina- 
tions are the carriers and distributors of the energy involved in the 
changes. 
CONCLUSION 
In summary, then, the metamorphic cycle may be regarded as 
indicative of a great pulsational alteration of the earth’s surface, 
kept going through the running down of energy and its escape from 
the earth, the cycle being an expression and vehicle of this running 
down of energy. ‘This cycle involves reversals of processes which 
keep the rock materials within certain limits of mineral condition 
and distribution, but these reversals are not quite compensating, 
with the result that there is a residual accumulation and redistribu- 
tion of certain substances such as sediments, schists, and gneisses, 
and salts of the sea. Some of the accumulations are definitely 
known, some are inherently probable, some are merely suspected. 
If there is truth in this general conception of the net results of 
metamorphic cycles, the study of metamorphism may become some- 
what prognostic if we use it to direct our search for some of these 
larger cumulative results which are now obvious in detailed work. 
