480 
Van Rise—Earth Movements. 
-cation of the earth began at the center, in advance of the sur¬ 
face, as conjectured by Hopkins, 1 this conclusion would probably 
hold, for it is hardly probable that consolidation did not also begin 
at the surface long before the earth was completely solidified. 
Whenever consolidation finally began at the surface the process 
outlined would take place. When a protruding continent had 
formed, and afterwards what is now the bed of the ocean had 
solidified, it was heavier than the continental masses, because 
the lightest material had already passed from a liquid condition. 
Another cause for the formation of the continents is suggested 
by an experiment made by Daubree. 2 He painted parts of the 
surfaces of an inflated rubber ball in patterns. Part of the 
nir was then allowed to escape, and it was found that the un¬ 
painted parts of the ball contracted radially more than the 
painted portions, the unpainted portions thus forming synclines, 
and the painted portions forming anticlines. This was attrib¬ 
uted to the greater stiffness of the painted portions. Where 
on the surface of the earth considerable areas of rock at first 
solidified, there would be greater stiffness, and hence this cause 
would operate, and tend to develop the continental masses 
and the oceanic areas. This supposed difference in stiffness 
of different parts of the earth’s surface may not have been of 
great importance, but it possibly produced some effect, working 
in conjunction with other causes. 
The above explanations of the origin of the continents are 
based upon the supposition that the earth was once in a liquid 
condition. Chamberlin, 3 however, questions the existence at 
any time of such a liquid earth. He suggests that the earth 
may have segregated from a meteoric swarm, so slowly that the 
temperature at the surface was at no time sufficient to liquefy 
the rocks. Under this theory he thinks that the continental 
elevations and oceanic depressions are caused by the readjust¬ 
ments of various kinds of the heterogeneous materials during 
the slow growth of the earth. 
1 Loc. cit., pp. 45-49. 
a Geologie experimental, by A. Daubree: Vol. I, 1879, pp. 585-590. 
8 A group of hypotheses bearing on climatic changes, by T. C. Cham¬ 
berlin: Journ. of Geol., Vol. V, 1897, pp. 670-675. 
