The first achievement under Prince Henry's guidance was the final rediscovery and colonization of Porto Santo and Madeira in 1418-25 by Gonsalvez Zarco, Tristam Vaz, and Bartholomew Perestrelo.[385] This work occupied the prince's attention for some years, and then came up the problem of Cape Bojador. The difficulty was twofold; the waves about that headland were apt to be boisterous, and wild sailor's fancies were apt to enkindle a mutinous spirit in the crews. It was not until 1433-35 that Gil Eannes, a commander of unusually clear head and steady nerves, made three attempts and fairly passed the dreaded spot. In the first attempt he failed, as his predecessors had done, to double the cape; in the second attempt he doubled it; in the third he sailed nearly two hundred miles beyond. [Footnote 385: Perestrelo had with him a female rabbit which littered on the voyage, and being landed, with her young, at Porto Santo, forthwith illustrated the fearful rate of multiplication of which organisms are capable in the absence of enemies or other adverse circumstances to check it. (Darwin, _Origin of Species_, chap. iii.) These rabbits swarmed all over the island and devoured every green and succulent thing, insomuch that they came near converting it into a desert. Prince Henry's enemies, who were vexed at the expenditure of money in such colonizing enterprises, were thus furnished with a wonderful argument. They maintained that God had evidently created those islands for beasts alone, not for men! "En este tiempo habia en todo Portugal grandisimas murmuraciones del Infante, viendolo tan cudicioso y poner tanta diligencia en el descubrir de la tierra y costa de Africa, diciendo que destruia el reino en los gastos que hacia, y consumia los vecinos del en poner en tanto peligro y dano la gente portoguesa, donde muchos morian, enviandolos en demanda de tierras que nunca los reyes de Espana pasados se atrevieron a emprender, donde habia de hacer muchas viudas y huerfanos con esta su porfia. Tomaban por argumento, que Dios no habia criado aquellas tierras sino para bestias, pues en tan poco tiempo en aquella isla tantos conejos habia multiplicado, que no dejaban cosa que para sustentacion de los hombres fuese menester." Las Casas, _Hist. de las Indias_, tom. i. p. 180. See also Azurara, _Chronica do descobrimento e conquista de Guine_, cap. lxxxiii.] [Illustration: Portuguese voyages on the coast of Africa.] [Sidenote: Beginning of the modern slave-trade, 1442.] [Sidenote: Papal grant of heathen countries to the Portuguese crown.] [Sidenote: Advance to Sierra Leone.]