At Bury and at Quarry Bank the two brothers were unresting in their efforts both to acquire knowledge for themselves and to communicate it to their neighbours. They delivered courses of lectures, and took boundless trouble to make them interesting and instructive. In these lectures William Greg took what opportunities he could find to enforce moral and religious sentiment. 'I lay it down,' he said, 'as an indubitable fact that religion has double the effect on Saturday that it has on Sunday; and weekday morality, incidentally introduced, meets with far more attention than the tautology of Sabbath subjects, treated in the style in which they generally are by professed teachers.' A more questionable diligence displayed itself in the zealous practice of experiments in animal magnetism and mesmerism. With a faith that might have moved mountains the two brothers laid their hands upon all sorts of sick folk, and they believed themselves to have wrought many cures and wonders. William Greg described animal magnetism as a 'discovery bearing more immediately and extensively on the physical happiness of the world than any which the last three centuries have witnessed.' The cowardice of doctors and others, who believed but were afraid to speak, stirred all the generous fire of youth. 'Here, of itself,' he cries out to his sister (September 4, 1829), 'is a bitter satire upon human nature, and a sufficient answer to all who moralise on the impropriety of flying in the face of received opinions and public prejudice. I assure you it is a knowledge of how often the ridicule and contempt of the world has crushed truth in the embryo or stifled it in the cradle, which makes me so eager to examine and support those opinions which mankind generally condemn as visionary and irrational.' In later times these interests became a bond between W. R. Greg and Miss Martineau. He finally let the subject drop, with the conviction that years of practice had brought it no farther on its way either to scientific rank or to practical fruitfulness. The time would have been better spent in severer studies, though these were not absent. From Green Bank he writes to his sister in 1830:--
Sam and I are at present engaged in some calculations on population, which have brought us to a very curious, beautiful, and important conclusion hitherto overlooked by all writers on the subject whom I have consulted, and which threatens to invalidate a considerable part of Malthus's theory. It respects the increase or diminution of fecundity; but I will write you more fully when we have quite established our facts. I have just finished a number of very tedious tables, all of which confirm our conclusions in a manner I had not ventured to anticipate....