PORTO RICO or PUERTO RICO, as originally written, is an island of the United States of America. It is the most easterly of the Greater Antilles, situated between 17° 50' and 18° 3o' N., and between 65° 3o' and 67° 15' W. It has for its northern boundary the Atlantic ocean, for its southern the Caribbean sea, for its western the Mona Passage, and for its eastern the Virgin Passage. It is situated about 7o m. E. of the island of Haiti, and about 4o m. W. of the island of St. Thomas, one of the Virgin islands and about 1,400 m. S.E. of New York city. It is nearly rectangular, with an average length from east to west of about ioo m. and a width of 35 to 4o miles. Its approxi mate area is 3,435 sq. miles.
The island is the eastern extremity of a chain extending east and west over r,000 m. and the northern extremity of a chain of smaller islands over 600 m. in length reaching to the northern coast of South America. These islands are the summits of submerged mountain ranges. The deep-sea soundings north of Porto Rico disclose one of the most profound chasms on the globe, known as "Brownsons Deep." It measures more than 27,00o feet. The surface of Porto Rico consists of plains from the mountains to the sea, while the interior and much the larger portion of the area consists of an irregular series of mountain ranges, the highest rising to an altitude of over 4.000 feet. These ranges extend from east to west across the island, but are broken in formation, with intervening valleys of sur passing fertility and beauty. The rivers are not navigable except for a short distance from the coast, but afford an abundance of water-power, and a supply for irrigation of the coastal plains and for the towns. The coastal plains are narrow on the southern slope. The principal mountain ranges are of the same geological period and of similar origin. They are of mixed volcanic and sedimentary formation, consisting chiefly of hornblende, gneiss and tuff, embedded in which at the higher altitudes are masses of blue limestone of the Cretaceous period. There is much under ground drainage, the rivers often disappearing in chasms to reappear at a distance. Many of the mountains are honeycombed
with caves, in some of which are found interesting Indian relics.
Gold mines were worked in the mountain regions and in the beds of the streams for some years in the first century of the Spanish conquest. According to official statistics, 2,700 lb. of gold were shipped to Spain from 1509 to 1536. This was prob ably the part belonging to the Crown of Spain, being one-fifth only of the amount secured. Some is still to be obtained by washing in the streams, but regular work has long been abandoned. Silver, lead and copper in small quantities were also discovered. Magnetic iron is found in many places in large quantities. It is of high grade and contains over 6o% of metal. Transportation difficulties alone seem to prevent development. Manganese is sent to the States in considerable quantity. Marble deposits of the highest quality are found in large quantities. Granite is also found suitable for building. Limestone, gypsum, clays suitable for brick, tile and rough ceramics are abundant. Kaolin of superior quality suitable for the manufacture of porcelain is also found. No coal nor oil has so far been discovered. For the most part the mountain ranges are covered by erosion deposits forming a soil of deep, reddish clay loams and tenacious red clays. So cohesive and compact are these soils that they are maintained even in almost vertical positions. Cultivation is pos sible and profitable even to the tops of the mountains.
Porto Rico is situated just within the torrid zone, hut its climate is hardly tropical. The mean January temperature for the island as a whole is 73° F, and the mean July temperature is 79°, a range of only 6°. The highest afternoon temperature is 86° and the lowest night temperature 68°. In the city of San Juan the highest temperature recorded is 94° and the lowest 62°. The mean annual temperature for Porto Rico is 76.5°. The coastal plains have a somewhat higher average of about 78°. In the higher interior regions the mean temperature varies from 70° to 76°, according to the elevation above sea-level. The diurnal change in temperature from day to night is from 6° to 7°.