228 PREVAILING THEORY CONCERNING [Ch. XI 



as one of its leading principles ; by which the stratified rocks 

 are said to have been forced up from their original horizontal 

 position, and inclined at various angles ; by which they have 

 been curved and contorted ; and by which they have also 

 been rent and fissured in various directions : thus affording 

 space for the intrusion of igneous rocks, in the forms of veins 

 or dykes, and for the formation of mineral and metallic veins; 

 and also occasioning those faults and dislocations so common 

 both in the stratified and unstratified rocks. To this doc- 

 trine, also, we cannot give our assent in toto. No one can 

 deny, that volcanic fires have in former times occasioned, and 

 still continue to produce, great mechanical alterations in the 

 structure of the solid crust of our planet; but it does not 

 appear to be satisfactorily demonstrated, that the inclination 

 of the primary strata is attributable to this cause ; nor, that 

 the phenomena of granitic veins and dykes, and of metallifer- 

 ous veins, are infallible indications of igneous convulsions. 



These are grave and weighty points of dissent, as regards 

 the stability of the Plutonic theory; and, if we can only 

 succeed in the first instance, in giving plausible reasons for 

 this difference of opinion, the objections ought surely to 

 receive a candid and patient examination : they may be 

 satisfactorily answered, or they may, perchance, prove knotty 

 and stubborn opponents. In either case, it may be requisite 

 to make appeals to nature by additional investigations: so 

 that there is some satisfaction in thinking, that, in whichever 

 way this discussion may terminate, by thus digging about and 

 examining the ground of the radical doctrines of the science, 

 the field of geology, like that of the departed husbandman 

 in Bacon's fable, may be rendered more fertile and pro- 

 ductive. 



In conducting the proposed enquiry, it is intended to 

 arrange it under the following heads : 



1. Are the primary schistose rocks stratified? 



2. Have the primary schistose rocks been elevated into 

 their present inclined positions by Plutonic agency ? 



