1254 
blance of the eruptive rocks and the petrographic provinces near 
the opposed shores, to lend support to the above interpretation. 
Still, in any case the resemblance of the rare eruptive rocks, is 
striking. According to Wreener the present coastlines of Africa and 
South-America represent the borders of a fissure, which is supposed 
by that writer to have gratually widened to the present Atlantic 
Ocean through horizontal movements of the two present continents. 
This hypothesis is at variance 
with the view that the Atlantic 
Ocean should have arisen through 
the subsidence of a continental 
region, while Africa and America 
are supposed not to have moved 
in a horizontal direction. 
The vertical movements executed 
on the surface of the earth are 
evidenced e.g. by upheaved shore- 
terraces and reefeaps, drowned 
river valleys etc. In connection 
with this the genesis of sea-basins 
is explained by vertical downward 
movements, because the horizontal 
movements are not established in 
| a similar manner and consequently 
eN escape our direct observation. But 
with rising rows of islands the 
| horizontal component of the rate 
of movement is sometimes much 
greater than the vertical one. The 
latter is distinguishable by up- 
Fig. 2. An older African fault- heavedecoralreefsand shore-deposits 
system. whereas the former must be derived 
cscs: The old Pilandsberg vulcano from far less distinguishable phe- 
(Transvaal). nomena such as the form of the 
reefcaps and the character of the 
fault-movements.*) The mesozoic 
rows of islands of the Tethys have 
executed chiefly horizontal and far less significant vertical movements, 
— —- Dikes of (nepheline) syenitic 
rocks. 
Scale + 1: 1100.000. 
1) H. A. Brouwer. Uber die horizontale Bewegung der Inselreihen in den 
Molukken. Nachr. Ges. der Wiss. zu Göttingen. 1920, Math. phys. Kl. Id. Breuken 
en Verschuivingen nabij de oppervlakte van bewegende geantiklinalen. Versl. Kon. 
Akad. v. Wet. Amsterdam, XXVIII, 1920, p. 1151. 
