518 T. C. CHAMBERLIN 
out the older systems of doctrine founded on a more mobile earth 
into a fairly complete working scheme of inquiry and elucidation. 
There were indeed individual instances in which the view of an 
elastico-rigid earth was entertained and yet regarded as springing 
from an earlier gaseo-molten state. But while thus entertained, 
this conception of an elastico-rigid earth was not carried out into 
a working system of doctrines consistent throughout with itself. 
There never grew out of it a panoply of tenets on which the geologist 
could base working hypotheses suited to his special problems on 
clear lines free from confusion with the tenets that sprang from a 
visco-solid earth. The instructor in geologic philosophy was never 
able to point the embryo geologists under his training to a set of 
views built distinctly on the working hypothesis of an elast co- 
rigid earth. 
But aside from this deficiency, as already remarked, a quite 
ample system of tenets, with alternatives and divergences, has been 
developed, covering the full range of conceptions from the picture of 
an earth with a thin shell and molten interior through various grades 
of partial solidity up to dominant visco-solidity of a high order of 
rigidity. 
So familiar have most of these tenets become that they often 
seem to stand by themselves quite independent of the hypotheses on 
which they were founded. By long currency they seem to have lost 
much of the speculative elements that really enter into them. This 
is not only a source of danger in itself but is likely to stand in the 
way of an impartial adjudication of less familiar conceptions that are 
not more speculative but merely seem to be so, and which are per- 
haps guarded by a more frank recognition of the speculative 
elements. 
The strong support which new evidences from cognate sciences 
lend to the doctrine of an elastico-rigid earth, in distinction from a 
visco-solid earth or any form of fluidal earth, adds emphasis to the 
need for a system of tenets that are strictly loyal to the elastic 
principle. While the principles are thus loyal, the working 
hypotheses must obviously recognize that, though the earth may be 
dominantly an elastico-rigid body, it is not exclusively so. The 
gaseous and liquid elements are factors of moment and co-operate in 
