~ 
266 Pennsylvania before and after the Elevation [March, 
logical problems with great reserve. While he welcomes all aid 
from this quarter for his difficult tasks, he should not allowa 
mathematical deduction of the kind above mentioned to prevent 
his acceptance of a contradictory physical deduction from ob- 
served facts. If the latter warrant any inference out of harmony 
with the former, there is at least a possibility that the latter may 
be right. And in our discussions regarding the interior of the 
earth we are in this condition. The data of the problem are as 
yet too obscure and uncertain for the mathematical engine, and 
physical deductions from observation claim and deserve at least 
_ equal consideration. 
If then the facts here detailed justify the interpretation put 
upon them, they lead to conclusions which, if admitted by a few 
geologists, have certainly not been generally asserted. If these 
indications of contraction are acknowledged to the full extent 
here given, or even to any considerable portion of that extent, 
they require admissions and lead to conclusions for which all are 
not prepared, and to which not a few will be strongly opposed. 
If the eastern seaboard of North America has, by tangential pres- 
sure, been shortened so that a line originally 153 miles long now 
_Measures only sixty-five miles, the circumference of the earth 
must be lessened to that extent. Consequently the admission of 
the statement here made involves an admission that the diameter 
of the earth was diminished by about one-third of this amount, 
or that. its radius was shortened thirteen miles by contrac- 
tion during the later part of the Paleozoic era. Geology is not 
fully prepared for this conclusion, and astronomy is perhaps less 
ready for it. Yet, unless one or the other can find some better 
explanation, the unwillingness to admit is not a sufficient reason 
for rejecting it. 
It is not the object of this paper to consider and discuss the 
_ various objections that must arise to the conclusion above stated. 
_ And such discussion would require more space than can be here 
occupied. A few words in conclusion must suffice. 
Possibly, though in treading on so uncertain a ground and in so 
dim a light I wish to advance with the greatest caution, aware 
that every step may be in the wrong direction, yet possibly there 
_ are indications to be found elsewhere which may render the infer- 
~= Ence above drawn a litile less startling, even if they do not bring 
ay within the bounds of oe, credibility. Spasmodic action with 
