3092 THOMAS C. CHAMBERLIN 
developed as will form the groundwork for this next stage of the 
work, which will be a study of the megadiastrophism of the earth. 
The introduction of the new term, megadiastrophism, calls for 
an explanation, if not an apology. It has already been found 
desirable by dynamic geologists to introduce the word “dias- 
trophism,’’ as a term of more comprehensive meaning than 
‘“‘deformation.”” The latter, while general enough in its etymo- 
logical sense, has come to have a rather special meaning, by 
reason of its long usage to designate folding, faulting, and similar 
declared distortions of strata. It is not usually understood to 
denote those more intimate changes of form that take place in the 
deeper interior of the earth’s body. To try now to make it 
include these would be at the risk of misinterpretation. But the 
new term diastrophism may be used to cover any form of distortion 
of solid bodies, and thus meet an imperative need. 
There now arises a need for a still more comprehensive term 
which shall denote the diastrophism of the earth as a whole—or of 
large parts of it, such as continents and suboceanic segments— 
in a collective way without regard to the various special modes by 
which the diastrophism is effected. In the very nature of the 
case, the diastrophism of these great units will be composite and 
very complex, but we need to deal with them in a unitary way 
despite this complexity. The term megadiastrophism seems suit- 
able for this purpose. 
One of the most formidable obstacles in the way of bringing 
into actual use a new set of concepts where an old set has long 
had full possession of the thought, lies in the difficulty of really 
clearing the mind of all the incidental factors of the old concept, 
and of putting in their place a full set of the new. The difficulty 
does not lie so much with the main bold features of the new view as 
with the less obvious progeny of derivative concepts that must, 
in consistency, go out with the parent concept. In the study of 
any basal subject that has run far back into one’s past thinking, a 
large brood of derivative concepts is quite sure to have been drawn 
out, but their connection with the parent idea is quite likely to 
have become obscure or to have passed entirely out of consciousness, 
so that the setting aside of the parent idea does not automatically 
