256 Outlines of Geology. 



from beneath the slate, sometimes appearing as a felspar rock, 

 and sometimes like granular quartz, with a few mica crystals. 



The situation and characters of granitic rocks suggest some 

 theoretical considerations, partly of an abstract, and partly of a 

 general nature, to the most important of which I shall briefly 

 allude, not so much on account of any intrinsic importance which 

 they possess, as from the eagerness with which they have been 

 animadverted upon by the contending geological schools. 



The manner in which granite occasionally pervades the super- 

 incumbent stratified rocks ; the damage which it often does to 

 them at its veins and junctions ; the new inclinations which it 

 gives them ; and above all, its occasional protrusion in considerable 

 masses connected with veins, but above the slaty and generally 

 superposed rocks ; and its occasional embedded slaty masses, are 

 circumstances which give the Huttonian theory of its origin a 

 plausible aspect : while on the other hand, the delicate and well- 

 defined line of junction with which slate and granite sometimes 

 meet, the utter want of all fracture and violence at their contact, 

 but more especially the slow and imperceptible transition of gra- 

 nite into gneiss, of gneiss into mica-slate, and of mica-slate into 

 clay-slate, seem to favour the Wernerian view of its deposition. 

 When, however, we fancy that we trace its crystallization from a 

 fluid, we are suddenly recalled to the difficulty of conceiving any 

 fluid, much less of an aqueous nature, which could have dissolved 

 and deposited granite, which is so singular and complex a crystal- 

 line aggregate ; and though the notion of igneous fusion is not 

 without its concomitant weak and objectionable points, it is so 

 much more consistent with the phenomena, and even with experi- 

 mental deduction, as to find, with all its imperfections, a more 

 ready access to the mind of the unprejudiced observer. 



As all our strata are theoretically incumbent upon granite, 

 which we conceive to form the lowest part of the crust that 

 envelopes the globe, and which some have been bold enough to 

 assert as forming its nucleus, so experience teaches us that the 

 loftiest mountains in the world are composed of the same material, 

 and that the alpine chains of the four quarters of the globe, 



