314 SKY. GEOLOGY. RED SANDSTONE. 



the map. It must be remarked however, that if with most 

 geologists we suppose these beds to have been displaced 

 from a position originally horizontal, the present is no 

 criterion of the former thickness of the deposit. The re- 

 versed positions of the strata show that the points of eleva- 

 tion, (or of subsidence, since it is indifferent which is 

 assumed) have been situated in various places ; and it is 

 abundantly obvious, that a single operation of this nature 

 taking place in the middle of a horizontal mass would, when 

 the change to a high angle occurred, double the original 

 thickness. It will also be seen, that on this supposition 

 some of the alternations which here occur may be falla- 

 cious ; since if we assume, for example, two portions 

 of red sandstone in reverse order, lying on the two sides 

 of a vertical or intermediate bed of some other rock, 

 these may originally have constituted but one stratum; 

 the present appearance of alternation being merely the 

 result of the change of position. 



Although the preceding account terminates the history 

 of the principal mass of the red sandstone, there still re- 

 main two detached portions requiring notice. 



The least extensive of these is found at Loch Sligachan, 

 where it is seen lying at the foot of the syenite moun- 

 tains and consequently unconnected at one side with 

 any other regular rocks; while at the other it is imme- 

 diately followed in conformable order by the same lime- 

 stone that succeeds the principal mass, the direction and 

 dip of the whole being similar to those of that mass. 



The second portion is of somewhat greater extent and 

 more importance. It occurs on the shore at the foot 

 of Garsven, extending along- the sound of Soa for about 

 a mile, and ceasing soon after the coast turns to form 

 the entrance of Loch Scavig. Its breadth does not exceed 

 four or five hundred yards, and, as the mountain rises 

 suddenly from the water, it extends a few hundred feet 

 upwards on the declivity. As no other regular rocks are 

 here to be seen, its affinity with the other portions of 



