Correspondence—Professor Joseph Le Conte. 523 
CORRESPONDENCE. 
CONTINENT FORMATION. 
Srr,— Having just returned from my usual summer vacation trip 
to the mountains, I have only now seen the June Number of your 
MaGazrne containing Mr. Crosby’s article on “Continent Formation,” 
in which he criticizes the views of Prof. Dana and myself on this 
subject. No one can be more aware than myself of the extreme 
uncertainty of any views yet proposed on this most difficult subject. 
So far from objecting to such criticisms, therefore, I hail with 
pleasure anything whether in the way of advancement of new, or 
the criticism of old, views. My object in this communication is 
merely to correct what I conceive to be some misunderstandings. 
1. Mr. Crosby (p. 242) says, “According to Prof. Dana’s theory, 
the continents during the course of geological times have become 
higher and broader, and the oceans deeper and narrower. But jusé 
the reverse is an unavoidable deduction from Prof. Le Conte’s theory ; 
for as the refrigeration of the earth continues, the contraction along 
the longer or continental radii must, sooner or later, begin to gain 
on that of the shorter or oceanic radii, and from that moment the 
continents begin to subside beneath the surface of a universal ocean.” 
The italics are my own. 
I have two objections to make to this. (a) It is by no means 
“an unavoidable deduction,” wnless, while the conductivity on 
different sides were different, the coefficient of contraction were the 
same. But this is extremely improbable. (b) But even supposing 
the coefficient of contraction were the same, and that therefore 
“sooner or later” the inequalities would begin to grow less, it is 
quite evident that that time has not yet arrived, and probably will 
not while the earth is habitable. It is evident that the inequalities 
would increase to a limit which is yet far from being reached; for 
with the exception of a very thin crust, the mass of the earth is still 
incandescently hot. 
2. Again, Mr. Crosby says (p. 243), ‘These theories rest at outset 
on an assumption which is not supported by a vestige of evidence, 
viz. that the earth was originally, and is now, of unlike composition 
along different radii or on different sides.” ‘“ Where are the facts 
supporting it? Where are the analyses showing essential difference 
between continents and ocean-bottoms ?” 
In answer to this objection, I would simply say that Mr. Crosby 
overlooks the enormous size of the contracting body, and the com- 
parative minuteness of the deformation by contraction. The average 
difference between continental and oceanic radii is only three miles,* 
or ~es0 of the whole. In a globe of 2 ft. in diameter this would be 
less than ~3> of an inch—a difference too small to be perceived. 
Now I am quite sure that a ball of clay 2 ft. in diameter, turned to 
a true sphere while in a wet condition and allowed to dry, would 
deform by contraction more than this. I think that even a ball of 
1 Extreme elevations are due to mountain-making, not continent-making causes. 
