SKY. GEOLOGY. RED SANDSTONE. 307 



of dip and interchange of substances; but to describe 

 these would now only lead to fruitless repetition. It must 

 be remarked that with all this confusion the line of bear- 

 ing is still preserved with the greatest pertinacity, scarcely 

 varying a few degrees from the true one ; and, that, 

 whatever alterations occur in the dip, there is no cor- 

 responding change in the substances, which continue to 

 alternate without any regard to its variations. 



Crossing now this series in a south-easterly direction 

 towards the boundary of the gneiss, a great body of 

 red sandstone appears, occupying the highest ridge and 

 extending, as far as can be discovered, to the gneiss, 

 although the actual junction cannot be traced among 

 the incumbrances of the interior country. Its position 

 appears to be vertical, and it is accompanied by schist, 

 but in much less quantity than usual. This circum- 

 stance is important, since it thus follows, that in 

 this portion of the series, the common red sandstone is 

 found both in the highest and in the lowest position ; 

 while the schist, which in other portions was nearest to 

 the gneiss, is here transferred to the intermediate beds. 

 From this fact among others was deduced the remark, 

 that the beds change their composition even according to 

 the line of their prolongations. If the line of the lowest 

 portion of red sandstone now described be prolonged to 

 the north-east, it will be found to correspond with those 

 near the Kyle rich which consist of grey quartz rock 

 or indurated sandstone ; while similar inconsistencies will 

 occur in attempting the mutual prolongations of the other 

 substances. This remark is of little consequence in a 

 mineralogical view, since the composition of the quartz 

 rock and of the sandstone is nearly identical ; the differ- 

 ences consisting only in the very variable characters of 

 colour and compactness. Nor is the occasional absence 

 or presence of the schist a matter of surprise, as in many 

 other cases, similar beds vanish and reappear in the same 

 line, as they happen alternately to be enlarged or exte- 



