FitzRoy's formal assignment was to chart coastal waters, but his hobby — passion really — was to seek out evidence for a literal, biblical interpretation of creation. That Darwin was trained for the ministry was central to FitzRoy's decision to have him aboard. That Darwin subsequently proved to be not only liberal of view but less than wholeheartedly devoted to Christian fundamentals became a source of lasting friction between them.
菲茨罗伊的主要任务是绘制沿海水域图，可是他的爱好——实际上是极度的热情——是要为《圣经》中所描述的上帝创造人的文字寻找实证。达尔文曾经接受过神学训练，这是菲茨罗伊决定让他一同前往的主要原因。可是达尔文后来不但表现出自由主义的观点，而且并非全心全意地奉行基督教教义，这成了他们之间不断冲突的根源。

Darwin's time aboard HMS Beagle, from 1831 to 1836, was obviously the formative experience of his life, but also one of the most trying. He and his captain shared a small cabin, which can't have been easy as FitzRoy was subject to fits of fury followed by spells of simmering resentment. He and Darwin constantly engaged in quarrels, some "bordering on insanity," as Darwin later recalled. Ocean voyages tended to become melancholy undertakings at the best of times — the previous captain of the Beagle had put a bullet through his brain during a moment of lonely gloom — and FitzRoy came from a family well known for a depressive instinct. His uncle, Viscount Castlereagh, had slit his throat the previous decade while serving as Chancellor of the Exchequer. (FitzRoy would himself commit suicide by the same method in 1865.) Even in his calmer moods, FitzRoy proved strangely unknowable. Darwin was astounded to learn upon the conclusion of their voyage that almost at once FitzRoy married a young woman to whom he had long been betrothed. In five years in Darwin's company, he had not once hinted at an attachment or even mentioned her name.
达尔文在“贝格尔”号上从1831年一直待到1836年。显而易见，这对于他来说，这既是一次增长阅历的大好机会，也是一次充满艰辛和困苦的旅行。他和菲茨罗伊船长一起挤在一个小舱里，这很可能不是一件容易的事，因为菲茨罗伊经常大发脾气，接着又恨得咬牙切齿，他们经常争吵不休。达尔文后来回忆说，这种争吵有时几乎到了“疯狂的边缘”。远洋航行即使在最好的时候也往往是一件令人烦闷的事——“贝格尔”号的前任船长就是在孤寂与忧伤中用子弹对准头颅结束了自己的生命的——而菲茨罗伊来自一个著名的患有抑郁症的家族。10年前，他的叔叔卡斯尔雷子爵在其担任英国财政大臣的任期内用刀子割断了自己的喉咙。（1885年，菲茨罗伊也以同样的方式自杀身亡。）即使在情绪稳定的时候，菲茨罗伊也是不可理喻的。他们的远航刚刚结束，菲茨罗伊就和一个他爱慕已久的年轻女子结了婚，这使达尔文吃惊不小，因为在他们长达5年的朝夕相处的过程中，菲茨罗伊竟然一次也没有表露过他的这种爱慕之情，他甚至连她的名字也从未提到过。