146 MEXICO, CENTRAL AMERICA, WEST INDIES. 



forming its nortliern continuation, is separated from the mainland by a profound 

 channel where the waters of a coast current set steadily from south to north at a 

 velocity of two or three miles an hour. South of Cozumel the dangerous Chin- 

 chorro bank, as well as Arrowsmith on the north side, is also a coralline limestone 

 mass rising from the bed of a deep basin ; but the creeks, bays and other inlets 

 on the coast, especially those of E-spiritu Santo and Asuncion, are almost completely 

 choked with sands and reefs. 



The submarine pedestal of Yucatan begins at the north-east angle of the 

 peninsula, and extends over 125 miles northwards, thus embracing the island of 

 Mujeres and the cluster of islets in the vicinity of Cape Catoche. The escarp- 

 ment of the submarine bank, as indicated by the sounding line plunging suddenly 

 into depths of 100, 250, 1,000 and even 1,500 fathoms, thus describes a great 

 curve round Yucatan, roughly parallel with the coast. The still-submerged 

 portion is far more extensive than the upheaved peninsula itself, and may be 

 estimated at about 60,000 square miles. Should it ever rise above the surface of 

 the sea, it will present the aspect of an almost horizontal limestone mass, in its 

 general appearance exactly resembling the present peninsula. The numerous 

 cayos (cays or reefs) scattered over this submarine plateau, Alacran, Arenas, Los 

 Triangulos, Areas, are all coralline rocks similar to those fringing the coast of the 

 mainland, and all have their most active colonies of polypi on the outer face turned 

 towards the surf rolling in from the high seas. It was at the Alacran, or 

 "Scorpion," Reef that the Valdivia was wrecked in 1511, the crew escaping in a 

 longboat to the Yucatan coast near Cape Catoche. Geronimo de Aguilar, one of the 

 two survivors, afterwards became Cortes' interpreter during the conquest of 

 Mexico. 



The Arenas cays, near the south-west corner of the bank, consist of a few 

 islets frequented by myriads of aquatic birds and covered with guano. In 1854 

 the Mexicans first began to work these deposits ; they were followed by the 

 Americans, who claimed to be the first occupants, and on that ground pretended 

 that the cay belonged to the United States. This claim to a bank obviously lying 

 in Yucatan waters gave rise to long diploinatic discussions. 



ElVERS. 



The fluvial systems of East Mexico present in Chiapas and Yucatan a contrast 

 analogous to that of the relief of these regions. In Chiapas the running waters 

 flow in superabundance on the surface of the ground ; in Yucatan, water has to 

 be sought at great depths in the chasms of the rocks. I^ast of the Rio Tonala, 

 which forms the boundary between the States of Yera Ciuz and Tabasco, the 

 whole of the Atlantic slope as far as Yucatan belongs to the two united basins of 

 the Grijalva and Usumacinta, which rise in the same district on the Guatemalan 

 uplands and enter the Gulf of Mexico through the same channel. The Grijalva, 

 which flows under several different names at different parts of its circular course, 

 has its chief sources in the province of Huehuetenango, and the town of this name 

 is itself watered by one of its headstreams. After entering Mexican territory 



