remote the one from the other; that the Creator rested in his labor." Darwin was struggling with inconsistencies in these ideas. As they neared the end of the voyage his thoughts about the mockingbirds shook his confidence that species were fixed and that variation was limited. In Cape Town, South Africa, Darwin and FitzRoy visited John Herschel. On 20 February 1836, Herschel had written to Lyell praising his Principles of Geology as opening a way for bold speculation on "that mystery of mysteries, the replacement of extinct species by others." Herschel thought catastrophic extinction and renewal "an inadequate conception of the Creator", and by analogy with other intermediate causes "the origination of fresh species, could it ever come under our cognizance, would be found to be a natural in contradistinction to a miraculous process". The letter was widely circulated in London, and Darwin remembered the phrase "that mystery of mysteries". Missionaries were being accused of causing racial tension and profiteering, and after the Beagle set to sea on 18 June FitzRoy wrote an open letter to the evangelical South African Christian Recorder on the Moral State of Tahiti incorporating extracts from both his and Darwin's diaries to defend the reputation of missionaries. This was given to a passing ship which took it to Cape Town to become FitzRoy's (and Darwin's) first published work. FitzRoy too had seen geological features as supporting Lyell's timescale, and on his return to England extracts from his diary stressing the immense age of the Patagonian raised beaches were read to the Royal Geographical Society, but he married a very religious lady and in his Narrative of the voyage added a supplement regretting having "remarked to a friend" that these vast plains "could never have been effected by a forty days' flood", remarks he ascribed to his own "turn of mind and ignorance of scripture" during the voyage. Darwin's loss of faith In his later private autobiography, Darwin wrote of the period from October 1836 to January 1839: "During these two years I was led to think much about religion. Whilst on board the Beagle I was quite orthodox, & I remember being heartily laughed at by several of the officers (though themselves orthodox) for quoting the Bible as an unanswerable authority on some point of morality. I suppose it was the novelty of the argument that amused them. But I had gradually come, by this