But though the tendency of his researches in geology was mainly towards the investigation of the phenomena connected with changes in the outline of the surface, he did not neglect the study of minerals and rocks, in which he had been trained under Jameson. Previously to 1836, with the view of learning more of the history of ancient geological upheavals, he had examined " the trap rocks of our own island, the ophites of the Pyrenees, and the serpentines of Anglesea and the Lizard — the porphyries of Northern Italy — the granite veins of Mount's Bay and Glen Tilt — the ancient volcanoes of Auvergne, the Eifel, the Siebengebirge, and of Rome — and the modern volcano of Vesuvius." In December 1835 he gave to the Royal Society of Edinburgh a narrative of his researches in central France, dwelling more especially on the analogies between the volcanic rocks of that district and the trappean masses of his own country. Throughout his narratives of foreign travel, also, we everywhere meet with indications that, though busied with what had become his own more special branch of the science, he remained no indifferent observer of the rocks among which his journeys led him. He retained his fondness for mineralogy to the end. When I last saw him at St. Andrews he showed me a collection of veined agates which he had accumulated in the course of years, and with which he used often to beguile a little leisure in trying to speculate upon the manner in which the concentric siliceous coatings might have been formed.
In concluding this sketch of the late Principal's geological labours, I must not forget that some of his researches, though in themselves dealing with more or less distinctively physical questions, had often important geological bearings. Such were some of his meteorological investigations, and his carefully conducted experiments upon the temperature of the earth at different depths and in different soils near Edinburgh. These experiments were, I believe, the first made in this country, with any degree of precision, to determine the rate at which the temperature of the surface is conducted downwards, and the variations due to differences in the nature of the material through which the heat is transmitted.
Sir David Brewster was born at Jedburgh in December 1781, and had thus attained the advanced age of more than eighty-six years when he died in February of last year. During this long life his scientific activity was incessant, and the stream of his original papers, some 300 in number, flowed on without a check.
Nor did this singular fertility by any means exhaust Sir David Brewster's energies. He wrote in the Reviews frequently and well ; he edited the 'Edinburgh Encyclopaedia,' and shared in editing the ' Edinburgh Philosophical Journal,' the ' Edinburgh Journal of Science,' and the ' Philosophical Magazine.' He founded the Scottish Society of Arts, and helped to found the British Association ; he was Principal of St. Andrews, and afterwards of Edinburgh University ; he was long Secretary of the Royal Society of Edinburgh, and he died the President of that learned body.
