ANNIVERSARY ADDRESS OF THE PRESIDENT. 187 



at intervals by certain combinations, are questions for the solution 

 of which we have as yet no data to lead us beyond probable 

 inferences. It was long ago observed that when dykes of basalt 

 passed through sedimentary rocks, earthy limestones were frequently 

 changed into crystalline marble, shales into flinty slate, argillaceous 

 sandstone into jasper, and bituminous coal into graphite or cinder. 

 Similar changes were also often observed at the junctions of granite 

 with sedimentary rocks. An attentive observation of these phae- 

 nomena led Hutton to infer that the strata derived from the detritus 

 of pre-existing rocks had been consolidated into stone by the agency 

 of subterranean heat ; and although he extended his theory to all 

 the strata, to many which subsequent observations have shown it to 

 be inapplicable, still the germ of the modern theory of metamor- 

 phism is clearly seen in one of the fundamental positions of the 

 Huttonian theory of the earth. But sound as were the views of that 

 philosopher in his leading doctrines, they were adopted by a very 

 small number of geologists, so strongly had the theories and system 

 of Werner got possession of men's minds, especially in Germany 

 and France. About twenty years ago however some startling facts 

 were brought to light; we heard that Belemnites had been found in 

 micaceous schists in the Alps, and that an insensible passage could 

 be traced from a secondary oolite full of organic remains, to the 

 highly crystalline marble of Carrara, the old type of primary lime- 

 stone, and under circumstances which afforded the strongest pre- 

 sumptive evidence that the oolite had been changed into the marble 

 by the action of adjacent igneous rocks. Then there came facts on 

 a grand scale analogous to those that had been observed at the junc- 

 tions of trap dykes and granite veins with sedimentary rocks, and 

 not only extending to great distances from the igneous rocks, but 

 the secondary shales were changed into rocks that could not be di- 

 stinguished from the so-called primitive gneiss and mica-schists, and 

 like them included crystallized garnets. 



Mr. Lyell, in 1833, brought forward a more extended and com- 

 plete development of the Huttonian hypothesis of consolidation, and 

 first proposed the adoption of the term " metamorphic " to this pe- 

 culiar altered structure of sedimentary rocks, — a term which has 

 been since universally adopted ; and every year has disclosed new 

 facts from all parts of the world, in confirmation of the theory that 

 the older crystalline and indurated schists, limestones, dolomites 

 and quartzites, and many similar beds of more modern date, were 

 not deposited with a structure such as they now present, but were 

 accumulations of detrital matter, ti'ansformed into their present con- 

 dition mainly by the action of heat, accompanied by other chemical 

 action, and the powerful agency of steam and. elastic forces under 

 enormous pressure. A very ingenious process, invented by Mr. 

 Brockedon, described in a short paper read before us last year, by 

 which he converts, under very powerful pressure, the powder of 

 graphite into a solid mass having a conchoidal fracture, and un- 

 distinguishable from the most compact native bhick-lead, siiows 

 that pressure alone may convert fine detrital matter into solid stone. 



