482 CUMBKAY (GREAT). GEOLOGY. 



from the inevitable consequences of association, to 

 separate substances in other respects allied, to confound 

 together rocks differing in other more important parti- 

 culars, and to unite formations essentially distinct, by 

 one unessential and varying character. It is equally evident 

 that the relative position of any given series to the primary 

 rocks, does not in itself constitute an unvarying and 

 essential character ; as the partial nature of -the secondary 

 strata frequently causes the upper members of an exten- 

 sive deposit, or even those of different deposits, to 

 rest on these ; an example of which has already been 

 pointed out in Morven. The term of old red sandstone, 

 thus derived from position chiefly, appears in this way 

 to have been also an occasional source of obscurity and 

 confusion. 



It must already have been perceived that, in conse- 

 quence of these views, the primary strata of the Sand- 

 stone islands have been confounded with that series which 

 skirts the southern border of the Highlands, to which 

 this island, like the rest of these strata in the Clyde, 

 appertains. It will be a subject for the inquiry of others, 

 whether this series does not differ from the red sandstone 

 of England also, as well as from analogous deposits exist- 

 ing in other parts of the world. I need not recur to the 

 peculiarities by which it is characterized in Arran ; but 

 it is evident that the white sandstone, together with the 

 shale, limestone, and coal, are all portions of it ; and cha- 

 racters similar, if not equally perfect, will be found to per- 

 vade the whole tract. All these substances here alternate 

 with that red sandstone which they have been usually 

 supposed to follow as a distinct series, nor is there any 

 difference between the upper and lower members of that 

 deposit; a supposition which has been adopted for the 

 solution of this imaginary difficulty. If, in this particular 

 instance, the red colour be supposed unessential, a great 

 part of the difficulty vanishes ; although the coal and 

 limestone of the Arran series, will still appear sufficient to 



