332 RED PRIMARY SANDSTONE. 



primary, and those occurring in the secondary 

 classes, is often equally difficult. 



The alternations of red sandstone on the large 

 scale, are with gneiss and with quartz rock ; and 

 as it has hitherto been examined only on the 

 north-west coast of Scotland, the history of its 

 geological position is limited to the phenomena 

 there visible. Under this system of alternation, 

 it- occupies very extensive tracts, forming also 

 some of the highest mountains which Scotland 

 possesses. 



Although, in some places, its regular alter- 

 nation with the gneiss is distinctly perceptible, 

 in others it follows the strata of that rock in a re- 

 verse or unconforming position; being some- 

 times nearly horizontal where these are much 

 elevated. In these instances, the sandstone ap- 

 pears to be connected with the gneiss by ih in- 

 tervention of a conglomerate formed of fragments 

 of the latter, which, generally however, seems to 

 occupy a very limited spaced 



Where it alternates in a parallel manner with 



the gneiss, it is often found ito pass into ttet f 

 by an uiidefinable trahsition ; arid this is effected 



