182 
MAJOR EARTH FEATURES 
than the ocean bottoms. The former belong predominantly to 
the region of Sal, the others to that of Sima, as defined by Suess. 
Since the limit of extent of Sal and Sima on the earth’s surface 
seems to correspond essentially with that of the continental masses 
and the ocean basins, this fact would warrant a relative perma¬ 
nence of the two major forms of the crust. 
In striking contrast to these results of geophysical researches 
stand certain paleogeographic investigations, since they seem in 
many cases to require, between continents, land connections which 
later have sunk into the abyssal deeps of the world-sea. These 
land bridges have been postulated by many paleogeographers to 
such an areal extent for the Paleozoic and Mesozoic eras that 
the present relationship of land to water over the earth’s surface 
has been changed completely around. Especially is this true in 
the reconstruction of the distribution of land and sea during 
Mesozoic times, in which almost all paleogeographic works show 
a gigantic land-mass in the southern hemisphere, extending from 
the east coast of South America over Africa and the East Indies 
to the west coast of Australia. 
The hypothesis of the sinking of such extensive masses of salic 
rocks in the region of Sima is contrary to the results of the 
gravity measurements on the oceans.® Wegener ® has recently 
undertaken to reconcile the demands of the paleogeographers 
and the geophysicists by seeking to explain the major features 
of the earth’s surface genetically through the theory of the hori¬ 
zontal movement of the continental masses. For the hypothesis 
of the sinking of former land connections he substitutes the 
theory of the splitting off and horizontal shifting of the salic 
continental masses which, so to speak, swim on the zone of Sima, 
and whose surfaces in general coincide with the floor of the great 
world-sea. In this way the Atlantic ocean arose, through the 
splitting off of America from Europe-Africa, and in like manner 
anterior India and Australia, together with Antarctica, were cut 
off from the African mass and the two former lands shifted to 
the northeast into their present position. The beginning of the 
8 The late Prof. Joseph Barrell lefti an unpublished paper on this subject, showing 
how a lighter crust can be loaded sufficiently to sink it into oceanic depths; see “The 
Evolution of the Earth and its Inhabitants,” p. 43, 1918. 
9 Die Entstehung der Kontinente: Petermanns Geog. Mitt., I Bd., pp. 185, 195, 253- 
256, 306-309, Gotha, 1912; also, Geol. Rundschau, III, pp. 276 - 292 , 1912. 
