But agriculture in the near future will certainly not be the main industry of the island. For there are known to be gold, copper, iron, zinc and coal mines, which have never been developed. In fact, strange as it may appear, none of these valuable mines is worked at all. The vegetable productions have been considered so valuable that in order to cultivate them the minerals have been neglected. There are also extensive sponge fields, which are very valuable, but which have not been touched, owing to several causes, chiefly the lack of capital. The same can also be said of the quarries of white stone, granite and marble.
Then there is the question of salt, which is sure to be of importance. There are large quantities of salt obtained from the lakes. Salt works have been established at Guanica and Salinas, on the south coast, and at Cape Rojo, on the west. This constitutes the principal mineral industry of Porto Rico.
Hot springs and mineral waters are found at Juan Diaz, San Sebastian, San Lorenzo and Ponce, but the most famous are at Coamo, near the town of Santa Isabella.
It is now interesting to see what the trade of Porto Rico has been with other countries, and especially the United States during recent years.
A very large part of the island's trade has been carried on with the United States, where corn, flour, salt-meat, fish and lumber have been imported in return for sugar, molasses and coffee.
The natives are not a sea faring people, and care little or nothing for ships of their own. Therefore, by far the larger part of their trade with other countries has been carried on by the means of foreign ships.
Porto Rico has paid into the Spanish treasury about 4,000,000 pesos annually, which is equivalent to about $800,000.
In normal years, that is, when no war was going on, the total value of imports into the island amounted to about $8,000,000, and the exports to about $16,000,000.
The latest Spanish statistics, that is, during 1896, give the importations into Porto Rico as amounting to $18,945,793, and the exports to $17,295,535.
The average entrances of ships into the ports have been 1919 vessels of an aggregate of 327,941 tons, of which 544 of 81,966 tons were British. Articles of import have been distributed by countries as follows: