142 ACCOUNT OF mt ROCKS NEAR DUNDEE.' 



transition, which, I think, I have observed in other 

 plac-es. 



From the preceding description, it will appear^ 

 that many changes have taken place in the posi- 

 tion of these beds of sandstone and claystone 

 since the period of their formation. But, of the 

 cause of these dislocations or slips, we are entire- 

 ly ignorant. The situation of the strata of sand- 

 stone in the basin-shaped cavity of the porphyry^ 

 makes us acquainted with a fact in the history of 

 stratification, of the greatest importance. The 

 abettors of the vulcanic hypothesis contend, that 

 all the strata of rocks were originally deposited in a 

 horizontal position. The fact before us, is in opposi- 

 tion to such an opinion. The strata in the bed of 

 porphyry are nearly horizontal, whereas the strata 

 of sandstone are highly inclined, being parallel 

 with the sloping sides of the basin. If we sup- 

 pose one of the sides of this cavity removed, and 

 the inclined strata on the other side of the cavity 

 left behind, a superficial observer would be ready 

 to conclude, from such partial appearances, that 

 these inclined strata had been moved into theiic 

 present angular position by an ascending move- 

 ment of the inferior bed of porphyry. Instances 

 frequently occur to every practical mineralogist, 

 where highly inclined strata thus rest upon the ine- 

 qualities of the fundamental rock, which, to all ap- 

 pearance, has never been moved. The disciples of 

 the German school embrace the opinion, that in 



