264 BULLETIN OF THE 



ancient and older plateaus, which, when their limestone cap is finally 

 removed down to the metaniorphic base, will assume the Villa Clara 

 type. 



The drainage system of Cuba is extensive. In general the streams 

 flow from the central axis toward the opposite coasts, and are of the type 

 which modern geographers would term simple consequent or autogenous 

 streams. They have light-colored blue water like that of the limestone 

 springs of Florida and Texas, and in many cases obtain their supply 

 from the undeiground waters of the limestone region. Where seen 

 throughout the interior upland plateaus of Cuba they are small in 

 volume, and flow in slightly indented channels in wide valleys, and are 

 remarkably free from the incisions of lateral drainage. A typical stream- 

 way is shown on Plate IX. They do not possess deep barrancas or 

 canons until they begin to cut across the edge of the CuchiHa plateaus 

 near the coast. In many cases these rivers are intermittent, disappear- 

 ing into and reappearing from the cavernous limestones. As they ap- 

 proach the escarpments of the coastal platforms, they reach the sea either 

 by sinking into tlie limestone, by tumbling cascades, or by cutting deep 

 vertical caiions. They are all slightly tidal at their mouths, the salt 

 water extending at high tide a short distance up them, but never reach- 

 ing far inland of the soboruco. Most of them bring down to the coast 

 the metamorphic and igneous rock of the old nucleal foundation, Init in 

 no case have I observed limestone fragments, although the rivers must 

 degrade and transport in solution far more lime than any other material. 

 The vertical canons in some cases, like that of the Yumuri of the east, 

 extend to the sea, and testify to the rapid rising of the land, confirming 

 the story of the cliffs and base levels as will be described later. (See 

 Plate I. Fig. 6.) 



Perhaps the most important factor in the evolution of the topographic 

 conditions of Cuba is the superficial and underground destruction and 

 alteration of the limestones by solution, lieretofore mentioned. Owing 

 to the porosity of the limestone rocks, the drainage of Cuba is largely 

 underground in the limestone regions, and flowing surface streams and 

 lateral drainage channels, such as the dendritic headwater ramifications 

 so common elsewhere, are notably scarce in the higher region inland 

 from the coast, and the upland limestone region seems to be dissolving, 

 rather than oorrading, into a sink-hole topography of vast fjroportions. 



The Coastal Topography. — None of the topographic features of Culia 

 are so peculiar as the innumerable subcircular harbors^ which indent its 



1 See Agassiz, Bull. Mus. Comp. Zoul., Vol. XXVI. No. 1, Tlates XIII., XIV. 



