Earthquakes are also very frequent, the last of great importance having occurred in 1863, 1880, 1892, 1894, and 1897. In 1897 a tremendous tidal wave affected the Island of Leyte, causing great destruction of life and property. A portion of Tacloban, the capital of the island, was swept away, rendering it necessary to extend the town in another direction. In the wet season the rivers swell considerably, and often overflow their banks; whilst the mountain torrents carry away bridges, cattle, tree trunks, etc., with terrific force, rendering travelling in some parts of the interior dangerous and difficult. In the dry season long droughts occasionally occur (about once in three years), to the great detriment of the crops and live-stock. The southern boundary of the Archipelago is formed by a chain of some 140 islands, stretching from the large island of Mindanao as far as Borneo, and constitutes the Sulu Archipelago, the Sultanate of which was under the protection of Spain (_vide_ Chap. xxix.). It is now being absorbed, under American rule, in the rest of the Archipelago, under the denomination of Moro Province (q.v.). CHAPTER II Discovery of the Archipelago The discoveries of Christopher Columbus in 1492, the adventures and conquests of Hernan Cortes, Blasco Nunez de Balboa and others in the South Atlantic, had awakened an ardent desire amongst those of enterprizing spirit to seek beyond those regions which had hitherto been traversed. It is true the Pacific Ocean had been seen by Balboa, who crossed the Isthmus of Panama, but how to arrive there with his ships was as yet a mystery. On April 10, 1495, the Spanish Government published a general concession to all who wished to search for unknown lands. This was a direct attack upon the privileges of Columbus at the instigation of Fonseca, Bishop of Burgos, who had the control of the Indian affairs of the realm. Rich merchants of Cadiz and Seville, whose imagination was inflamed by the reports of the abundance of pearls and gold on the American coast, fitted out ships to be manned by the roughest class of gold-hunters: so great were the abuses of this common licence that it was withdrawn by Royal Decree of June 2, 1497. It was the age of chivalry, and the restless cavalier who had won his spurs in Europe lent a listening ear to the accounts of romantic glory and wealth attained across the seas. That an immense ocean washed the western shores of the great American continent was an established fact. That there was a passage connecting the great Southern sea--the Atlantic--with that vast ocean was an accepted hypothesis. Many had sought the passage in vain; the honour of its discovery was reserved for Hernando de Maghallanes (Portuguese, Fernao da Magalhaes).