THE HUMAN OR PRESENT PERIOD. 523 



water of the ocean when all the continents are lifted some thousands 

 of feet, and because of a special difficulty of this kind involved in the 

 fact that these valleys descend into closed basins such as the deeper 

 parts of the Mediterranean and Caribbean seas and the Gulf of Mexico, 

 which might naturally be supposed to retain so much of their waters 

 as lies below the lowest notch in their rims however much they were 

 carried up by epeirogenic movements. There are also difficulties con- 

 nected with the forms and the gradients of the valleys. 1 The views 

 of deformation outlined on previous pages (Vol. II, pp. 233-235) afford 

 a different mode of interpretation, in which lateral movement plays 

 a larger part, and vertical movement a lesser part, and in which the 

 warping of the border of the continents replaces a movement of their 

 general mass. This interpretation also embraces other border phe- 

 nomena which need to be noted before the interpretation itself is 

 offered. 



Upward warping near the coasts. — Nearly every coast is bordered 

 by inlets which are almost invariably submerged valleys; but, fol- 

 lowed inland, these inlets usually graduate into deep sluggish rivers, 

 and these, farther inland, are very often replaced by rapids or falls, 

 or at least by steepened gradients. When the continental borders are 

 examined throughout their full extent in all latitudes, the prevalence 

 of this phenomenon becomes impressive. The chief exceptions are 

 the great rivers which drain interior basins through broad gaps in 

 the elevated tracts that so generally border the continents, as the 

 Mississippi, which issues through the great gap between the Appa- 

 lachians and the mountains of Arkansas and Indian Territory, and the 

 Amazon, that issues between the Parima and the Brazilian mountains. 

 A critical study of the gradients of the normal coast-border river- 

 channels, embracing at once the submerged portions, the inlet por- 

 tions, and the high-gradient portions, indicates a warping rather than 

 a simple uplifting and depression, such as is implied in the epeirogenic 

 conception. This is an important factor in the alternative interpre- 

 tation. 



The apparent imperfection of the geologic series on the continental 

 borders. — It is most logical to infer that, as the continents were already 

 outlined as early as Paleozoic times, persistent accumulation of sedi- 



1 Kiimmel, Jour. Geol., Vol. Ill, 1895, p. 367. 



