Scarcely had Darwin taken his pass degree at Cambridge when the great event of his life occurred which, more than anything else perhaps, gave the final direction to his categorical genius in the line it was thenceforth so successfully to follow. In the autumn of 1831, when Darwin was just twenty-two, it was decided by Government to send a ten-gun brig, the 'Beagle,' under command of Captain Fitzroy, to complete the unfinished survey of Patagonia and Tierra del Fuego, to map out the shores of Chili and Peru, to visit several of the Pacific archipelagoes, and to carry a chain of chronometrical measurements round the whole world. This was an essentially scientific expedition, and Captain Fitzroy, afterwards so famous as the meteorological admiral, was a scientific officer of the highest type. He was anxious to be accompanied on his cruise by a competent naturalist who would undertake the collection and preservation of the animals and plants discovered on the voyage, for which purpose he generously offered to give up a share of his own cabin accommodation. Professor Henslow seized upon the opportunity to recommend for the post his promising pupil, young Darwin, 'grandson of the poet.' Darwin gladly volunteered his services without salary, and partly paid his own expenses on condition of being permitted to retain in his own possession the animals and plants he collected on the journey. The 'Beagle' set sail from Devonport on December the 27th, 1831; she returned to Falmouth on October the 2nd, 1836.