12 POPULAR SCIENCE MONTHLY. 



an American innovation, and for the same reasons. We have here 

 better opportunities for studying both the newer and ohk-r topo- 

 graphic forms, developed over broader geographical domains, and 

 surmounting geological formations commonly of wider extent, so that 

 the evolution of geomorphic features from the simple to the complex 

 form is more easily understood. The explorations of the sub- 

 merged topography are also along more favorable lines than in the 

 older world. The many repetitions of the middle geological forma- 

 tions in western Europe, and the favoral:)le opportunities they afford 

 for studying certain fossils and minerals, have also distracted from 

 the development of geomorphy there, while in America the investi- 

 gations of the physical features are now occupying the most promi- 

 nent place among geologists. 



Former Changes of Level in the West Indies. — The Lesser 

 Antilles, or Windward Islands, have often been regarded as a chain 

 of sunken mountains, and the Greater Antilles as having been con- 

 nected with the mainland. But the dissimilarity of their features, 

 compared with those of our northern continent, and the almost gen- 

 eral absence of the higher types of animal life in the islands, caused 

 many to question such connections in late geological times. How- 

 ever, more analytical methods have brought about different con- 

 clusions. 



The doctrine of the permanency of the ocean basins in the West 

 Indian region received its coup de grace by the discovery of radio- 

 larian earths upon the highest land of Barbadoes, which was eluci- 

 dated in the classic treatise of Messrs. A. J. Jukes-Browne and J. B. 

 Harrison.* Radiolaria are minute organisms with beautiful silicious 

 shells, which are now forming geological accumulations at only 

 great oceanic depths. Similar deposits also occur in Trinidad, Cuba, 

 Hayti, Jamaica, and probably other islands. They furnish testi- 

 mony of the upheaval of the floor of the ocean from depths of two 

 miles or more. The age of the radiolarian earths in the West Indies 

 appears to have been about the early Miocene period, which was con- 

 siderably prior to the building and completion of the West Indian 

 continent. These deposits are most interesting, as they show, upon 

 biological evidence, the uplifting of the bed of the ocean, and later 

 on we shall show that an equally great terrestrial movement occurred 

 in the opposite direction, upon the sinking of the Antillean continent 

 in Pleistocene times. 



Modern Changes of Level Measured. — Such great earth 

 movements are slow pulsations extending over large continental 



* The Geology of Barbadoes. Quarterly Journal of the Geological Society of London, 

 vol. xlviii, pp. 170-226. 



