The admiral, therefore, on the 11th of August, set sail eastwards, and was borne along swiftly by the currents. On the 13th, he anchored near to the strait; and on the following day, towards noon, the ships approached the _Boca del Drago_. The mouth of this formidable ocean-pass is about five leagues wide; but there are two islands lying between its extremities. The immense body of fresh water which flows through the gulf in the rainy season, meeting the incoming waves, causes a terrific commotion extremely dangerous to ships; and this was the first occasion on which vessels were to go through it. The great navigator had neither chart nor pilot to guide him; but fortunately no sunken rock obstructed his way, and the current of fresh water prevailing over the incoming waves carried him safely through.[A] Columbus now shaped his course to the westward, along the outer coast of _Paria_, which he still supposed to be an island; and he was borne still further unconsciously on the same course (whilst he lay to at night in order to avoid running on rocks and shoals) by the Gulf Stream which sets across the Caribbean Sea. It took some time for him, with all his experience, to realise the fact that this great body of fresh water, brought by the rivers to the ocean, could not be the outcome of mere islands, but must proceed from the _Terra Firma_ which was the object of his search. On leaving the coast of _Paria_, the navigator saw to the north-east, at some distance, in succession, the islands of _Tobago_ and _Granada_, which form part of South America; but here we must for the present take leave of the great sea-king;[B] for the limits of this work merely include the continent of South America and the islands immediately belonging to it. As the minute study of American geography does not form part of the education of every one, it may be proper to remark that the geographical limits of South America are perfectly distinct from those of the various countries forming Central America, as well as from the islands of the Spanish Main. The next Spanish navigator who appeared in these seas was the celebrated Alonzo de Ojeda, who had accompanied Columbus in his second voyage, being then but twenty-one years of age. Through the influence of a cousin of his own name, a Dominican friar, he had obtained from Bishop Fonseca a commission, authorising him to fit out an armament, and to proceed on a voyage of discovery, provided that he should not visit any territories belonging to Portugal, nor any lands discovered for Spain before 1495. It was stipulated that a certain proportion of his profits should be reserved for the Crown.