358 GEOLOGICAL APPEARANCES 



iiess in all these substances recurs upon us ; and the advocates 

 of an igneous theory cannot pretend to furnish a satisfactory 

 explanation of these, as well as many other more common 

 phenomena of a primary country, till they have acquired a far- 

 ther knowledge of the properties of bodies composed of fel- 

 spar, quartz, hornblende, carbonate of lime, mica, &c. when 

 subjected to high temperatures, and regulated cooling, — with 

 compression also, where there is any volatile ingredient. It is 

 to an igneous theory, however, that we may look with the 

 most confident hope, and it seems in vain to expect as- 

 sistance from any hypothesis of aqueous solution and depo- 

 sition. 



133. The various inferences, for which I have been contend- 

 ing, have been separately considered, both for the sake of keep- 

 ing the argument distinct, and because I conceive the evidence 

 to be much stronger in favour of some, than of others. The 

 whole hypothesis may be briefly expressed thus : That the sie- 

 nite, in a state of igneous fusion, was impelled from below, bj 

 a violent force, against the strata ; that it bent them, broke 

 them, dispersed them, and filled up the intervals, which it now 

 occupies ; that the fragments of the strata were in some degree 

 softened by the heated sienite, so as to admit of a mutual ac- 

 tion ; that, while the whole intermixed mass was still soft, 

 some farther dislocation took place in it, and that all this, oc- 

 curred under a great confining pressure of incumbent matter. 

 This hypothesis coincides, in the main, with ihat by which Dr 

 Hutton explained the phenomena in Glen Tilt, in a paper 

 read before this Society in the year 1790, and published in its 

 Transactions. If it differs widely from the speculative views 

 concerning these phenomena, which have been more recently 

 o-iven by Professor Jameson and Dr Macknight, I must leave 

 it to the candid inquirer to decide between us ; but, if I have 



differed 



