Neither the exact cause, nor the precise time of the decline of the belief in the righteousness of slavery can be defined. It was doubtless due to a combination of causes, one probably being as indirect as the recognition of the greater economy of free labor. With the decline of the belief the abolition of slavery took place." The institution of slavery was actually existent in Christian Scotland in the 17th century, where the white coal workers and salt workers of East Lothian were chattels, as were their negro brethren in the Southern States thirty years since; they "went to those who succeeded to the property of the works, and they could be sold, bartered, or pawned". (1) "There is", says J. M. Robertson, "no trace that the Protestant clergy of Scotland ever raised a voice against the slavery which grew up before their eyes. And it was not until 1799, after republican and irreligious France had set the example, that it was legally abolished." 1 "Perversion of Scotland," p. 197. 2 "Capital and Wages ", pp. 15, 16. Take further the gain to humanity consequent on the unbelief, or rather disbelief, in witchcraft and wizardry. Apart from the brutality by Christians towards those suspected of witchcraft, the hindrance to scientific initiative or experiment was incalculably great so long as belief in magic obtained. The inventions of the past two centuries, and especially those of the 18th century, might have benefitted mankind much earlier and much more largely, but for the foolish belief in witchcraft and the shocking ferocity exhibited against those suspected of necromancy. After quoting a large number of cases of trial and punishment for witchcraft from official records in Scotland, J. M. Robertson says: "The people seem to have passed from cruelty to cruelty precisely as they became more and more fanatical, more and more devoted to their Church, till after many generations the slow spread of human science began to counteract the ravages of superstition, the clergy resisting reason and humanity to the last". The Rev. Mr. Minton concedes that it is "the advance of knowledge which has rendered the idea of Satanic agency through the medium of witchcraft grotesquely ridiculous". He admits that "for more than 1500 years the belief in witchcraft was universal in Christendom", and that "the public mind was saturated with the idea of Satanic agency in the economy of nature". He adds: "If we ask why the world now rejects what was once so unquestioningly believed, we can only reply that advancing knowledge has gradually undermined the belief". In a letter recently sent to the _Pall Mall Gazette_ against modern Spiritualism, Professor Huxley declares,