226 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1917. 



have been cut when the land was at least 100 feet higher with 

 reference to sea level than at present. The Cuban harbors are pouch- 

 shaped drainage basins into which the sea has been admitted by 

 submergence of the land. Plate 36 illustrates the basin of Yumuri 

 River and the gorge through which it flows into the sea near 

 Matanzas, Cuba. A slight lowering of the land would convert 

 this basin into a pouch-shaped harbor. There are living coral reefs 

 off the shores of Antigua, St. Thomas, and Cuba, and they have 

 evidently grown upward since the submergence of the former shore 

 lines of those islands. Shore-line phenomena such as these occur 

 around many of the West Indian Islands, along the coasts of Nica- 



Fig. 9. — Chaut of tart of bast coast of Antigua. From U. S. Hidrographic Chart 



No 1004. 



ragua and Honduras in Central America and along that of Brazil. 

 Instances of similar phenomena may be seen in Xew Caledonia, the 

 Society, Fiji, and other islands of the Pacific, and along the Queens- 

 land coast, landward of the Great Barrier Eeef of Australia. 



Where the surface of the land is underlain by limestone, rain water 

 that falls on the earth, instead of eroding stream ways and valleys, 

 in making its way back to the ocean may produce caves and solution- 

 wells by dissolving the limestone because of the carbonic-acid gas 

 it contains. In many areas, such as the Bermudas, the Bahamas, and 

 in places in southern Florida, caverns and solution-wells are found be- 

 low sea level. Text figure 11 (p. 228) , a cross section from the shore of 



