.564 'MULL. GEOLOGY. 



on the contrary appear to conform to the primary strata ; 

 a circumstance which, incorrectly observed, has occa- 

 sionally been a source of error in geological observations. 



The next diagram* shows more distinctly, that the 

 conglomerate and sandstone which form the secondary 

 set of strata, are deposited on the faces of the primary, 

 and that having filled the cavities which these may con- 

 tain, they assume first the horizontal and ultimately the 

 reverse position, their prolongations over the edges of 

 the strata becoming by inference unconformable.f The 

 last sketch J will show how such a stratified rock may 

 be actually conformable or otherwise, and it may be con- 

 sidered as a representation of these rocks before Inch 

 Kenneth was separated from Mull, one portion being 

 actually visible in the former island, and the other in 

 the latter. It is obvious from this statement that non- 

 conformity is not a test of distinction between the primary 

 and secondary strata. 



One general conclusion may be drawn respecting the 

 mode of connexion between the primary stratified rocks 

 and granite, from the manner in which the secondary 

 strata are deposited on the primary. I have shown that 

 the irregularities of the gneiss in Lewis, and the similar 

 cavities formed by the re-entering angle which lies between 

 the sides and ends of the primary strata in this place, are 

 filled with the conglomerate or secondary rock, which, as 

 soon as it has attained a level, becomes regularly stratified ; 

 proving that it has been deposited in a gradual manner on 

 a surface previously irregular. This is unlike the phe- 

 nomena at the granite junctions, where every thing is 

 disturbed and broken : repose, in short, marking the one 

 and the reverse the other. 



* The drawings from which these diagrams were constructed, are real 

 views of different points on the shores of Gribon at the junctions of the 

 conglomerate and the primary strata. 



f Plate XX. fig. 7. J Plate XX. fig. 6. 



