512 GARVH ISLAND. GEOLOGY* 



stance, while they are also preceded and followed by 

 it. The Whiten head affords an opportunity of tracing 

 the superposition of the gneiss to the quartz rock, with 

 similar exactness ; a clear section, with the definite con- 

 tact of the two, being there visible to those who will 

 hazard the risk of landing on this dangerous and rocky 

 shore. Thus the series of Loch Eribol consists of lime- 

 stone succeeding to quartz rock and gneiss, and followed 

 by the same substances in a regular order of super- 

 position. 



In retracing the whole of the series from Garvh 'island, 

 the sequence is found to be as follows : gneiss, limestone, 

 gneiss, quartz rock, limestone, quartz rock, gneiss ; and 

 to render the whole more intelligible a section is sub- 

 joined.* No hesitation can therefore exist in considering 

 the limestone of this district as primary ; since although 

 any doubt should remain respecting the quartz rock, 

 there can be none with regard to the gneiss ; it being a 

 part of that extensive mass which constitutes the greater 

 portion of the north-west of Scotland. 



In treating of Garvh island, I suggested the possibility 

 of its rocks having once contained organic remains. In 

 whatever light that conjecture may be viewed, their actual 

 existence is ascertained in one of the beds of Loch Eribol. 

 The rock in which they are found is not indeed calcareous, 

 but the geological consequences that follow are the same, 

 while the interest is rather increased by the peculiarity of 

 its nature. It is a porous, or incompact, granular quartz, 

 alternating with the beds of limestone, and appearing to 

 have contained calcareous matter which has been subse- 

 quently removed from the surface, where alone it is ac- 

 cessible, by the rains ; a case analogous to that of the 

 limestone of Diurness before described. In this rock, 

 conical bodies not exceeding a quarter of an inch in length, 

 are seen imbedded ; being evidently the fragments of 



Plate XXXII. fig. 1. 



