INTKODUCTION. 105 



iiii!; of iibyssmal dei)osits, described by Messrs Jukes-Browne and Harri- 

 son,'f'' and showing; «2;reat clianges of level in one direction, he was led to the 

 conclusion tliat the great depth of the drowned valleys is not inconsist- 

 ent with their lluvial origin, and this opinion has been sustained by more 

 recent discoveries regarding their connections with existing and buried 

 river channels of the continents and islands. It has been found that these 

 fjords are not exceptional or scattered, but numerous and apparently 

 connected into systems of drowned valleys. In order to extend our 

 knowledge of the connection between the Antilles and the continent, and 

 to obtain evidence as to when the connection existed the field-work was 

 carried from the continent to the Greater Antilles with success beyond 

 expectation. The later geology of that region proved that with minor 

 modifications the terrestrial movements of the coastal plain of the con- 

 tinent, so admirably set forth by Mr W J McGee,t extended to the West 

 Indies. The geographic history of Jamaica was not explained by the 

 government geologists, J; but their excellent data, as also those of Dr W. 

 M. Gabb§ in San Domingo and Costa Rica and the more scanty surveys 

 in Central America, all contain considerable material for extending gen- 

 eralizations based on discoveries in Cuba and the southern states (where 

 the writer has done much work) over the whole Antillean region. These 

 generalizations are further justified by the distribution of life in the 

 waters of the West Indies. 



Geomorphy as exemplified in Valleys. 



In northern regions the geologic broom of the Ice age swept over the 

 hills and filled the valleys so as to greatly obscure the to])Ography pro- 

 duced by meteoric agencies. Farther southw^ard the atmospheric forces 

 have left their record deeply engraved in the surface rocks. From the 

 study of land features it would appear that the forms of the valleys are 

 largely independent of the geologic undulations of the region, and that 

 open valleys (and sometimes those closed into basins) are to a great ex- 

 tent the direct result of atmospheric erosion. For exami)le, over the 

 plains of both the coast and interior, valle3's from a few rods to many miles 

 in width may either follow the strike of the rock strata of the country 

 or may cross their strike at any angles. In the southern Appalachians 

 numerous valleys follow the direction of the ridges, which- is generally 

 that of the strike, and at first sight appear to occupy mountain folds. 



♦"GcoloKV of Bftrbadoes," Quar. Jour. Geol.Soc. London, vol. xlvii, 1891, pp. 197-250, and vol. xlviii, 

 1892, pp. 17<>--.'26. 



t'*The Liilayette Formation," 12tli Ann. Rep. U. S. Gcol. Survey, 1892, pp. ■.n~-')2\. 



J"GeoloKy of Jamiiif'.a," by J. G. Sawkins, 18C9. 



g "Geology of San Doiningo,'' Trans. .\m. Phil. Sue., vol. xxv, 1873. "Geology of Costa Rica," Am 

 Jour. Sci., vol. viii, 1874, p. 388, and vol. ix, 1873, pp. 198,320; also manuscript in arciiives of tiie U.S. 

 Geol. Survey 



