In 1773 Williams took a house in Lawrence Street, Chelsea, married Mary Emilia, a woman without a fortune, and set up a school. As the fruit of his ministry he published a volume of "Sermons, chiefly upon Religious Hypocrisy" (1774). His educational ideas, founded on those of John Amos Comenius, he embodied in his "Treatise on Education" (1774). Book-learning he subordinated to scientific training based on a first-hand knowledge of facts. He made a novel application of the drunken helot plan, obtaining from a workhouse a 'lying boy' as an object lesson. His school 'prospered beyond his expectations', but the death of his wife (in 1774) for a time unmanned him. He tore himself away, 'leaving his scholars to shift for themselves', and 'secluded himself in a distant country' for 'many months'. He went to Buxton, according to some accounts; he never returned to Chelsea.