72 
HAYFORD. 
are seldom shaken so severely by earthquakes as to disturb 
our comfort. If the earth were stronger the stresses would 
accumulate for a longer time and to a greater intensity be- 
fore failure took place; but when failure took place it would 
be much more apt to bring disaster, by violent shocks and 
large changes of elevation ; therefore the more firmly you 
are convinced that the earth is so weak as to be failing con- 
tinuously, the safer you should feel. 
It is important to know whether the earth is a failing 
structure or not, because such knowledge is necessary to a 
true understanding of a many of the phenomena observed 
upon the earth. For example, it is a standard idea of the 
text-books, and indeed of many of the specialists in earth- 
sciences, that the flattening of the earth at the poles, its 
ellipticity, indicates that it was formerly a liquid earth, or 
is now a liquid earth with a thin crust. If the solid earth 
is a failing structure in the sense and to the extent that I 
believe it to be, said standard idea is nonsense. 
To those who are endeavoring to make progress in the 
study of the earth, it is especially important to know the 
true answer to the question, “Is the earth a failing struc- 
ture?” 
If the answer is “No;” if the earth is, in the main, a com- 
petent elastic structure, subject only to minor and local 
failure, then future progress will be made largely by the 
elasticians, by those who study the earth as an elastic struc- 
ture, as did Darwin, for example, in the investigation fre- 
quently referred to to-night. 
On the other hand, if the true answer is “Yes;” if the 
earth as a whole is a failing structure, failing frequently or 
continuously, failing in many parts; if failure is the rule 
rather than the exception, then future progress in studying 
the earth is reasonably certain to be made mainly by investi- 
gating the manner of failure. These investigations cannot 
be effectively made by mathematics applied to the laws of 
elasticity. The elasticians may furnish rough guides, may 
indicate limits approached but not reached; but the real 
progress will be made by those who study the non-elastic 
