DE. BUTTON AND HIS THEOEY. 39 



admit of neither doubt nor dispute ; the metamorphic cha- 

 racter of the succeeding deposits, the gneiss and mica-schist 

 systems is equally clear, whether we suppose with Sir C. 

 Lyell, that the metamorphism was complete, or with Professor 

 Phillips,* that it was only partial. The derivative character 

 of the sedimentary strata is fully proved ; and the whole of 

 these propositions are only better understood, and more 

 firmly established, after having stood the test of half a 

 century of investigation. 



The most important and novel of the whole, the altered 

 character of the metamorphic roaks, has been demonstrated 

 by Sir James Hall's experiments, who, by pulverising chalk 

 and hermetically sealing it, so as to prevent its gases from 

 escaping, and then exposing it to heat, converted it into 

 crystalline marble ; the very result presumed to have 

 occurred in nature, by the hypothesis of Dr. Hutton. In 

 a practical point of view, the fluid nature of granite was 

 considered to be proved by the investigations of the author 

 himself, who discovered in Grlen Tilt veins of granite, rami- 

 fying into superincumbent rocks, in a manner which could 

 only have been effected by a substance in a melted state, 

 a discovery which is said to have filled him with so much 

 delight, that his guides, says his biographer, conceived 

 that he must have discovered a mine of gold. His opinions 

 are farther conceived to be demonstrated by the passage 

 of these rocks into each other ; by the graduation of plu- 

 tonic into metamorphic deposits, and of the latter into 

 others of decidedly aqueous origin ; of granita into gneiss, 

 and of chlorite-schist and mica-schist into clay-slate, a fact 

 demonstrating the intimate relation of each, and the common 

 origin of all ; proving them to be what he declared them, 

 sedimentary deposits, altered by heat under pressure. 



Another individual, who has already been mentioned in 

 these pages, unassisted by the advantages of wealth, station, 

 or collegiate education, was laying down the basis of English 

 geology, by a series of the most laborious and practical obser- 

 vations. WILLIAM SMITH, a surveyor, by dint of unwearied 

 observation, and the natural powers of a strong mind, had 

 arrived at results similar to those obtained about the same 



* See his Treatise on Geology, in Lardner's Cyclopaedia, vol. i. p. 109. 



