468 Geological Society, 



The intimate friend of Hutton and of Playfair, he eagerly imbibed 

 the opinions of these celebrated men, and satisfied himself of the 

 leading truths in the Huttonian theory by extended and patient ex- 

 aminations of geological phaenomena, — not merely amongst the British 

 Isles, but in the Alps, in Italy, and in Sicily. The result of these 

 observations was communicated in a series of Memoirs read before 

 the Royal Society of Edinburgh, of which distinguished body he was 

 for many years the President. In alluding to these Memoirs, I at 

 once remind you how materially he assisted in demonstrating that a 

 certain class of granitic veins had been injected into the overlying 

 deposits posterior to their consolidation. He endeavoured to explain 

 experimentally the contortions of certain strata, and the manner in 

 which the phaenomena had been effected by upheaving forces acting 

 under compression. He subjected various rocks of igneous origin 

 to chemical analysis, and succeeded in establishing their relative de- 

 grees of fusibility. He gave an original and perspicuous account of 

 the true mode of formation of volcanic cones ; and whilst he pointed 

 out that Monte Somma was simply the segment of a vast volcano, 

 from the flank of which the present Vesuvius had arisen, he showed 

 the intimate analogy between the dykes of lava of the former and the 

 ancient trap-dykes of our continents. If, in tracing the revolutions 

 of the surface of the earth, he was led to attribute too much to the 

 influence of one great diluvial current, we must recollect that in this, 

 his only dereliction from the principles of Hutton, his conclusions were 

 founded on a striking class of phaenomena first observed by himself j 

 and that the diluvial theory (though in a modified sense) has still the 

 support of many of our most eminent geologists. To a mind so ac- 

 customed to speculate upon the intense energy of volcanic phaeno- 

 mena, it was a. natural inference that the fractures and dislocations 

 of mountain-masses have been produced by paroxysmal efforts of na- 

 ture, — in short, by mighty earthquakes, and their accompanying ele- 

 vations, depressions, and eruptions. 



Much, however, as we owe to him for his many accurate observa- 

 tions of nature, our debt of gratitude must specially be acknowledged 

 for his successful application of chemistry to geology, without which, 

 one essential condition of the theory of Hutton would not have been 

 established, as it now is, upon an immovable basis. The important 

 discovery of carbonic acid by Black, which was destined to lead 

 to the solution of many occult terrestrial phaenomena, was at first 

 cited by the Wernerians as destructive of the very basis of the theory 

 of the igneous consolidation of the strata of the earth, it appearing 

 impossible to explain the formation of crystalline marble from earthy 

 carbonate of lime, by the very agent which drives off the gaseous con- 

 stituent in every lime-kiln. To obviate this difficulty, the founder of 

 the new theory propounded, that the heat by which rocks had been 

 solidified was applied under enormous pressure ; that in consequence 

 effects had taken place entirely differing from those which manifest 

 themselves under the mere pressure of our atmosphere j and that 

 under such circumstances carbonate of lime might have been reduced 

 to a state of fusion without calcination. Though the genius of Hutton 



