The Culebrina river is bounded on the south and east by the Lares mountain ridge, and on the north by small hills of little interest.  From the Lares Mountains it flows from east to west and empties on the west coast north of San Francisco de la Aguada, in the center of the bay formed between Point Penas Blancas and Point San Francisco.

The Anasco river is formed by the Lares mountain ridge.  It rises in the eastern extremity of the mountains called Tetas de Cerro Gordo, flowing first northwest and then west, through the town of its name and thence to the sea.

The Guanajivo river has to its north the ramifications of the Lares ridge, to the east the Tetas de Cerro Gordo Mountains, and on the south Torre Hill.  In the interior of its basin is the mountain called Cerro Montuoso, which separates its waters from those of its affluent from the right, the Rosaria river.  It rises in the general divide, flowing from east to west to Nuestra Senora de Montserrat, where it receives the affluent mentioned, the two together then emptying south of Port Mayaguez.

The Coamo river is bounded on the west and north by the Sierra Grande, and on the west by the Coamo ridge.  It rises in the former of these sierras, and flowing from north to south it empties east of Coamo Point, after having watered the town of its name.

The Salinas river is bounded on the west by the Coamo ridge, on the north by the general divide, and on the east by the Cayey ridge.  It rises in the southern slopes of the Sierra Grande and flowing from north to south through Salinas de Coamo, empties into the sea.

Coasts, Harbors, Bays, and Coves.—­The northern coast extends in an almost straight line from east to west, and is high and rugged.  The only harbors it has are the following:  San Juan de Porto Rico, surrounded by mangrove swamps and protected by the Cabras and the Cabritas islands and some very dangerous banks; the anchoring ground of Arecibo, somewhat unprotected; and the coves of Cangrejos and Condado.  During the months of November, December, and January, when the wind blows with violence from the east and northeast, the anchorage is dangerous in all the bays and harbors of this coast, except in the port of San Juan.  Vessels are often obliged to put to sea on the menacing aspect of the heavens at this season, to avoid being driven on shore by the heavy squalls and the rolling waves of a boisterous sea, which propel them to destruction.  During the remaining months the ports on this coast are safe and commodious, unless when visited by a hurricane, against whose fury no port can offer a shelter, nor any vessel be secure.  The excellent port of San Juan is perfectly sheltered from the effects of the north wind.  The hill, upon which the town of that name and the fortifications which defend it are built, protects the vessels anchored in the harbor.  The entrance of this port is narrow, and requires a pilot; for the canal which leads to the anchorage,