222 Proceedings of the Royal Physical Society. 



and patience to read his " Essays." * This work, and his pre- 

 vious memoir, entitled, " Examination of the Supposed Igneous 

 Origin of Stony Substances," i* have long since passed out of 

 the familiar literature of Geology. They deserve, however, 

 to be remembered, if only because it was the appearance of 

 the memoir that stimulated Hutton to expand and republish 

 his " Theory " in the form in which he left it. 



Among Button's personal friends there were two who, 

 while earnestly and loyally sympathising with his doctrine, 

 had the ability to render it the most essential service. John 

 Playfair, the genial Professor of Mathematics in the Univer- 

 sity of Edinburgh, from constant intercourse with Hutton, 

 both in the city and among the hills, had thoroughly mastered 

 his friend's teaching. After Hutton's death in 1797, finding 

 that the Huttonian Theory still met with but little attention, 

 Playfair prepared and published his classic "Illustrations." J 

 Gifted with a pen as facile and graceful as that of his master 

 was heavy and obscure, he unfolded the new doctrine with 

 consummate skill, and produced a volume which will serve 

 as a perpetual model of luminous and fascinating exposition. 

 It was from the appearance of this work rather than of 

 Hutton's ponderous chapters that the real influence of the 

 Huttonian Theory began. 



Sir James Hall of Dungiass was a man of a wholly 

 different temperament. Quick, original, inventive ; with an 

 enthusiastic love of science, and a determination to take 

 nothing on trust, but to subject every statement where pos- 

 sible to the test of experiment, he became a follower of 

 Hutton, as it were against his will, and only by degrees, as 

 he succeeded in disproving one by one the objections which 

 at first the Huttonian Theory awakened in his vigorous mind. 

 He had travelled abroad. In particular he had visited some 

 of the volcanic districts of Italy, and had there seen the 

 phenomena of volcanic action partly under the guidance of 

 Dolomieu.§ Not long after the first publication of the 



* Geological Essays, 1 vol. 8vo, London, 1799. 



+ Memoirs of the Eoyal Irish Academy, vol. v. (1793), p. 51. 



X Illustrations of the Huttonian Theory of the Earth, 1vol. 8vo, Edin., 1802. 



§ Trans. Boy. Soc. Edin., v., 56. 



