“Men of very different characters, but all devoted to literature and science. This mutual intimacy has never been broken but by death, nor have any of the number failed to distinguish themselves in science or literature. Some may think I ought, with due modesty, to except myself. Mr Keir, with his knowledge of the world and good sense; Dr Small, with his benevolence and profound sagacity; ... Boulton, with his mobility, quick perception and bold adventure; Watt, with his strong inventive faculty, undeviating steadiness and bold resources; Darwin, with his imagination, science and poetical excellence; and Day, with his unwearied research after truth, his integrity and eloquence, proved altogether such a society as few men have had the good fortune to live with; such an assemblage of friends as fewer still have had the happiness to possess and keep through life.” There can be no doubt that Priestley’s coming to Birmingham contributed greatly to the interest of the meetings of the Lunar Society and reacted beneficially on Priestley himself by stimulating his activity and affording him the sympathy of congenial minds not less interested than he was in the study of natural science. As each meeting came round he was certain to find a gathering curious to hear of his latest experiments and eager to discuss with him their bearing upon the chemical doctrine of the period. Priestley’s influence and position in the Society may be inferred from the circumstance that almost immediately after he joined it Pneumatic Chemistry became one of the chief topics of discussion. This is amply demonstrated in the correspondence of its various members, which has been preserved to us in the biographies of Watt, Wedgwood and others, and in the scientific letters of Priestley, which have been collected and edited by Mr H. Carrington Bolton. One direct outcome of this interest is seen in Watt’s connection with the History of the Discovery of the Composition of Water. It is reasonably certain that if Watt and Priestley had not foregathered round the festive board of the Lunar Society, Watt would not have been stimulated to theorise on the meaning and true significance of Priestley’s experiments, and as to their bearing upon the fact that Priestley’s dephlogisticated air (oxygen) and inflammable air (hydrogen) enter into the composition of water. Watt’s claim to be considered as the discoverer of the composition of water rests upon his interpretation of the experimental phenomena made known to him by Priestley shortly after his arrival in Birmingham. The Water Controversy—a controversy which keenly excited the entire scientific world a generation or so ago—may be said to have arisen from the accident of Priestley’s removal to Birmingham and to his association with the Lunar Society.