Detrital Theory of Geology. 315 



internal structure ; and if not, yet the form, proportion, and 

 extent of the great mountain chains, or backbones of the 

 eartrj, our table-lands and steppes, ought to demand that 

 the formation of their physical construction be explained 

 independent of all ulterior facts that may hinge upon their 

 elucidation since careful induction, from well-known data, 

 can only lead to greater light and higher truths. 



From the foregoing reasons namely, ist, the gradual 

 increase of land over sea, which has been going on through 

 successive orders of strata ; and 2ndly, from the nature of 

 conformity in our mountain systems and table-lands, etc. 

 it is inferred that on the earth's surface we have nothing 

 lower in order of stratification than granite ; for if a lower 

 form of rock existed capable of transfusion between the 

 granite (and not veins and masses of particular forms of 

 melted granite), surely the conditions requisite for its trans- 

 fusion have been abundantly supplied both by the gradual 

 extension of the solid area of the globe, and also by the com- 

 paratively superficial depth at which the heat is located, and 

 which would have forced other matter above, in a manner suffi- 

 ciently plain so as to lead to no doubt as to its lower origin, 

 both from its own character and the extent of surface it would 

 occupy at different districts over the globe ; but granite is 

 evidently sufficiently thick and extensive under all circum- 

 stances to fill up, by its own melted substance, all cracks, 

 dykes, and fissures that may occur from the loss of continuity 

 in its own substance, as is continually seen in the vitrified 

 masses of granite running for miles in particular directions, 

 and materially interfering with the quarrying of granite in 

 the numerous Tors in this and other countries, and known 

 as " horse tooth." 



Hence the conclusion drawn is, that granite is the true 

 primary rock, and that trachyte, basalt, trap, or greenstone, 

 etc., etc., are but melted forms of- either granite or some one 

 or more of the metamorphic or secondary rocks, and that 



