THE METAMORPHIC CYCLE 307 
concentrating agencies with the common ones effecting the metamor- 
phism of the lithosphere as a whole. 
Stages in the partial redistribution of the elements above outlined 
appear in igneous rocks and in sedimentary rocks, so far as these 
have not become completely adapted to katamorphic conditions. 
Conglomerates, arkoses, and graywackes are largely in this class. 
Such partial changes are kaolinization, sericitization, and silicifica- 
tion of acid feldspars, or the alteration of basic feldspars by the devel- 
opment of epidote-zoisite, calcite, or prehnite and kaolin, or the 
change of augite to hornblende with separation of calcite, or of horn- 
blende to chlorite and epidote with separation of quartz and iron 
oxide. In fact, most described ‘‘metamorphic” changes are of this 
partial kind, and the fact is frequently lost sight of that the completion 
of the observed alteration means ultimately the development of the 
simpler minerals of the sediments. It does not follow that the deriva- 
tives of the authigenic minerals of the igneous rocks are in each case 
less complex chemically than the original mineral. Epidote is as 
complex as feldspar, hornblende as augite. But the change is — 
accompanied by the separation of other minerals that are less com- 
plex, such as kalin and calcite, and there is increase in volume 
when all end-products are taken into account, making the term 
“‘katamorphism” clearly applicable to the alteration. It may be 
emphasized that the long list of partial alterations of igneous rocks 
occurring in the upper part of the lithosphere are, with few excep- 
tions, katamorphic in this sense, that they are usually accompanied 
by a separation of varying amounts of the end-products of alteration 
observed in sedimentary rocks. This phase of the subject will be 
discussed in another paper. With this clearly in mind, the study 
and understanding of the alterations of igneous rocks in upper 
zones become simplified. 
In this connection, the question may be suggested: What are the 
broad differences between the metamorphism of surface volcanics 
and plutonic rocks, or between acid and basic rocks? It is not to be 
supposed that they alter equally in response to the demands of envi- 
ronment. Certain features of these differences are now known, but 
the subject has not yet been put on a systematic basis. 
Cementation.—No sooner do the sediments, the end-products of 
