It was, no doubt, mainly through Magellan that Priestley was brought into the society of that brilliant galaxy of men of science which at that period was the glory of France. In some respects he was out of sympathy with this environment, and, as he confesses, soon tired of Paris. Priestley never obtruded his religious convictions on any company he might be in; at the same time he never forgot that he was a Christian and a minister of religion. What is now called Agnosticism was at least as prevalent during the latter half of the eighteenth century as at any period of the history of Europe. Priestley tells us that a great part of the company he saw at Lord Shelburne’s did not really know what Christianity was, and Lord Shelburne numbered among his friends and political associates almost all who were intellectually eminent at that time in this country. He was not unprepared, therefore, to find that all the philosophers to whom he was introduced at Paris were unbelievers in Christianity and even professed Atheists. He was told, indeed, by some of them that he was the only person they had ever met with, of whose understanding they had any opinion, who professed to believe Christianity. It was this experience which caused Priestley to write his _Letters to a Philosophical Unbeliever_. He says that as he had conversed so much with unbelievers at home and abroad he thought he should be able to combat their prejudices with advantage. Indeed, he was wont to say that the greatest satisfaction he received from the success of his philosophical pursuits arose from the genuine weight it gave to his attempts to defend the principles of Christianity and to free it from those corruptions which prevent its reception with philosophical and thinking persons. Of the many advantages he enjoyed through his connection with Lord Shelburne, Priestley was always fully sensible. It came to him at the most opportune period of his career, and in the full tide of his intellectual vigour. The years he spent in this association were, so far at least as science is concerned, the most fruitful of his life. Lord Shelburne was a generous patron, and particularly encouraged Priestley in his chemical inquiries, affording him ample opportunity for their prosecution and defraying much of the expense they occasioned. He had pleasure in witnessing his experiments, and frequently requested him to exhibit them to his guests, particularly to foreigners, by whom a knowledge of Priestley’s work was thus spread abroad.