242 W. O. Crosby—Origin of Continents. 
a far stronger claim than the new to the title of the true theory of 
continents and ocean-basins. 
Many weighty objections to the modern theory have appeared 
in these pages within a few years. But it appears to the present 
writer that there are important arguments against this theory which 
have not yet been stated; and the object of this article is to bring 
forward some of these. Since, however, they bear with equal force 
against the theory advocated by Archdeacon Pratt and Prof. Joseph 
Le Conte, which differs in some important features from Prof. Dana’s 
theory, I will first contrast these two theories, before pointing out 
the defects common to both. 
The following statement of Prof. Le Conte’s theory is given in his 
own words! :—“ Continental surfaces and ocean-bottoms are due to 
unequal radial contraction of the earth in its secular cooling. It is 
evident that in such secular cooling and contraction, unless the earth 
were perfectly homogeneous, some parts being more conductive 
would cool and contract more rapidly in a radial direction than 
others. Thus some radii would become shorter than others. The 
more conductive, rapidly contracting portions, with the shorter radii, 
would become sea-bottoms; and the less conductive, less rapidly 
contracting portions, with the longer radii, land-surfaces. In other 
words, the solid earth becomes slightly deformed and the water 
collects in the depressions.” Le Conte and Pratt further hold that 
the quantity of matter along each of the terrestrial radii was not 
only originally, but is yet, essentially equal; “the matter being 
denser along the shorter oceanic than along the longer continental 
radii.” 
Certain passages in Le Conte’s writings lead one to infer that he 
regards his theory as essentially similar to Prof. Dana’s. Never- 
theless, the language quoted above shows that the difference is 
fundamental. They agree in requiring (1) an heterogeneous earth 
as a basis for unequal radial contraction, and (2) fixed continents 
and oceans; but beyond that they are diametrically opposed. For 
instance, Prof. Dana says that the more rapidly conducting and 
cooling areas form the continents; while Prof. Le Conte says they 
form the ocean-bottoms. Again, according to Prof. Dana’s theory, 
the continents, during the course of geological time, have become 
higher and broader, and the oceans deeper and narrower. But just 
the reverse is an unavoidable deduction from Prof. Le Conte’s 
theory; for, as the refrigeration of the earth continues, the con- 
traction along the longer or continental radii must sooner or later 
begin to gain upon that along the shorter or oceanic radii; and from 
that moment the continents begin to subside, and are ultimately lost 
beneath the surface of the universal ocean. 
Profs. Dana and Le Conte agree, however, upon the main point 
against which the following arguments are advanced, viz. that the 
continents and ocean-basins are permanent, their present positions 
being those which they occupied at the beginning of geological time. 
These theories rest at the outset upon an assumption which is 
1 Elements of Geology ; and Amer, Journ. Sci. (3) vol. iv. p. 382. 
