This is not an uncommon motive.

A man sees something that ought to be done, knows of no one that will do it but himself, and so is driven to the enterprise even should it be repugnant to him.
[Illustration: MAP OF WESTERN AFRICAN COAST.] IMPORTANT EXPEDITION Prince Henry, then, having once the well-grounded idea in his mind that Africa did not end, according to the common belief, at Cape Nam [Portuguese for "not"], but that there was a region beyond that forbidding negative, seems never to have rested until he had made known that quarter of the world to his own.

He fixed his abode upon the promontory of Sagres, at the southern part of Portugal, whence, for many a year, he could watch for the rising specks of white sail bringing back his captains to tell him of new countries and new men.
One night, in the year 1418, he is thought to have had a dream of promise, for on the ensuing morning he suddenly ordered two vessels to be got ready forthwith, and placed them under the command of two gentlemen of his household, Zarco and Vaz, whom he directed to proceed down the Barbary coast on a voyage of discovery.

A contemporary chronicler, Azurara, tells the story more simply, and merely states that these captains were young men, who, after the ending of the Ceuta campaign, were as eager for employment as the prince for discovery; and that they were ordered on a voyage having for its object the general molestation of the Moors as well as the prosecution of discoveries beyond Cape Nam.
DISCOVERY OF PORTO SANTO.
The Portuguese mariners had a proverb about the Cape, "He who would pass Cape Not either will return or not," [Quem passar o Cabo de Nam, ou tornara ou nam], intimating that if he did not turn before passing the Cape he would never return at all.

On this occasion it was not destined to be passed, for the two captains were driven out of their course by storms, and accidentally discovered a little island, where they took refuge, and which, from that circumstance, they called Porto Santo.