Marcu, 1893. ARE OCEAN DEPTHS PERMANENT? 181 
coasts are not outlined by folded structure, except in the arch of the 
Lesser Antilles, and in the corresponding short arch passing through 
Gibraltar, which serves to connect the mountains of north-western 
Africa with those of the south of Spain. These are what we may call 
the Pacific and the Atlantic types of oceanic regions. 
Indian geologists have shown how the immense Asiatic mountain 
waves, moving southwards against the Peninsula, have been dammed 
back by the resistent Peninsular mass, the Korana Hills, and the 
wedge-shaped mass of Assam; so that they actually form distinct 
arches, separated by deep angles receding to the neighbourhood of 
Tank, north of Dera Ismail Khan, to the Upper Jhelum and Brahma- 
putra Valley. In this case we call the Peninsula the ‘‘ Vorland.” 
Now cast a look on the map of the North Pacific, and compare 
the receding angles which mark the western and the eastern ends of the 
Aleutian arch, where it abuts against Kamschatka and North-West 
America. You will remark that this part of the Pacific is a ‘‘ vorland,” 
and homologous to the Indian Peninsula, whilst the Yellow Sea, 
Behring Sea, and others lie within the folded region. You may also 
examine the Mediterranean, and observe that the western half lies 
wholly within a curved and folded mountain chain (Apennines, Sicily, 
North Atlas, Gibraltar, Andalusian Cordillera), and that in the 
eastern half all the part south of Crete and Cyprus and east of Sicily 
lies on the African ‘“ vorland,” and the rest on the sunken parts of the 
Tauro-Dinaric arch. 
In the Atlantic region the mountain folds, as a rule, break off 
against the ocean (e.g., Brittany coast, Devon and Cornwall, south- 
west Ireland), or else have their folds facing’ away from the 
ocean, as in the case of the Alleghanies, and all other folded zones on 
the eastern side of North America as far as Newfoundland. The folds 
disappearing in south-west Ireland and in Brittany so very much 
resemble those rising from beneath the Atlantic on the coasts of Nova 
Scotia and New Brunswick, that M. Marcel Bertrand has ventured 
to publish a sketch-map, showing these chains trending right across 
the Atlantic. 
There exists a curious tendency for a depression or a sort of 
valley to form in front of the great folds facing the “ vorland.” For 
instance, the depressions of the African desert in front of eastern 
Atlas, the river valleys in front of the high Indian chains, and the 
Persian Gulf in front of the Zagros chains. Quite recently the 
Austrian exploring ship ‘“‘ Pola” found a depth of 4,400 metres near 
the south-west coast of Greece, near the front of the Dinaric arch; 
and some of the greatest oceanic depths show exactly the same 
position in front of the arches of Japan, the Kuriles, and the Aleutians 
with Alaska. This is the homology, for example, between the Ganges 
valley and the Tuscarora depth, both marking the limit of the folded 
ranges and the ‘“ vorland.” 
The structure of the earth’s crust does not, therefore, tell us that 
