of geological evidence led to various theories of an ancient Earth, and findings of extinctions demonstrated in the fossil geological sequence prompted early ideas of evolution, notably Lamarckism. In England these ideas of continuing change were at first seen as a threat to the existing "fixed" social order, and both church and state sought to repress them. Conditions gradually eased, and in 1844 Robert Chambers's controversial Vestiges of the Natural History of Creation popularized the idea of gradual transmutation of species. The scientific establishment at first dismissed it scornfully and the Church of England reacted with fury, but many Unitarians, Quakers and Baptists—groups opposed to the privileges of the established church—favoured its ideas of God acting through such natural laws. Contemporary reaction to Darwin The publication of Darwin's On the Origin of Species in 1859 brought scientific credibility to evolution, and made it a respectable field of study. Despite the intense interest in the religious implications of Darwin's book, theological controversy over higher criticism set out in Essays and Reviews (1860) largely diverted the Church of England's attention. Some of the liberal Christian authors of that work expressed support for Darwin, as did many Nonconformists. The Reverend Charles Kingsley, for instance, openly supported the idea of God working through evolution. Other Christians opposed the idea, and even some of Darwin's close friends and supporters—including Charles Lyell and Asa Gray—initially expressed reservations about some of his ideas. Gray later became a staunch supporter of Darwin in America, and collected together a number of his own writings to produce an influential book, Darwiniana (1876). These essays argued for a conciliation between Darwinian evolution and the tenets of theism, at a time when many on both sides perceived the two as mutually exclusive. Gray said that investigation of physical causes was not opposed to the theological view and the study of the harmonies between mind and Nature, and thought it "most presumable that an intellectual conception realized in Nature would be realized through natural agencies." Thomas Huxley, who strongly promoted Darwin's ideas while campaigning to end the dominance of science by the clergy, coined the term agnostic to describe his position that God's existence is unknowable. Darwin also took this position, but prominent atheists including Edward Aveling and Ludwig Büchner also took up evolution and it was criticized, in the words of one reviewer, as "tantamount to atheism." Following the lead of figures