no The American Geologist. February. 1901. 
the great mountain series on the western coast of North Amer- 
ica to a common origin is thereby prejudiced, instead of being 
supported. 
These three theories assign the earth-plan to a venerable an- 
tiquity ; but there is a fourth theory, which carries it back to an 
antiquity even more venerable. Lord Kelvin attributes the 
oceanic and continental areas to a chemical segregation in the 
gaseous nebula which was the parent of the earth. Accord- 
ing to this theory, "Europe, Asia, Africa, America, Australia, 
Greenland and the antarctic continent, and the Pacific, Atlantic, 
Indian and Arctic ocean depths, as we know them at present," 
were all marked out in the primaeval gaseous nebula. These 
gaseous continents condensed to liquid continents marked off 
from the sub-oceanic areas by chemical differences ; and these 
liquid continents were fixed as the solid continents, hightened 
by shoaling as the molten globe and its last lava ocean solid- 
ified. 
That theory appears probable with one verbal amendment 
— the substitution of the term "archean-blocks" for continents. 
That these archean blocks — the earth's great corner stones — 
were embryonically outlined by chemical segregations in the 
molten or gaseous stages of the earth seems probable. But 
these archean corner stones, though the foundations of the con- 
tinents, are not the continents. Lord Kelvin's theory suggests 
no explanation why chemical segregations should have as- 
sumed the shapes of the continents, so that his explanation 
rests on an unexplained cause ; and even if his theory be 
amended by application to the archean blocks instead of to the 
continents, the theory is geographically insufficient, as it does 
not show the relation between the archean blocks and the exist- 
ing continents. 
THE PERMANENCE OF CONTINENTS. 
That Lord Kelvin's nebulous segregations, Prof. Darwin's 
primitive wrinkline. Sir John Lubbock and Prof. Lapworth's 
double folds are all true causes seems probable. What is 
doubtful is whether any extensive trace of their influence can 
be discerned in the present distribution of land and water. A 
map of the world in early Cambrian times might show the in- 
fluence of these pre-geological incidents ; but their geographic- 
