EGG. GEOLOGY. 319 



stone. The western vein, which is the thinnest, possesses 

 no colours but the blue and black, the latter being found, 

 as in the eastern one, at the sides, where it is in contact 

 with the trap : I shall hereafter point out an analogous 

 circumstance in the island of Lamlash. No other veins 

 of this substance have been found in Egg, but it is not 

 unlikely that some exist about the eastern and least acces- 

 sible parts of the island. This opinion is deduced from 

 observing on the beach near Eilan chastel rolled stones of 

 a black pitchstone porphyry, quite unlike the produce 

 of these veins, and considerably different from the mass 

 of that rock which forms the Scuir, the most remarkable 

 as well as the last substance in the order of superposition. 

 The Scuir* of Egg occupies a position somewhat 

 easterly and westerly on the southern side of the island. 

 It forms a long and curved ridge resembling an irregular 

 wall ; which, generally speaking, may be considered as 

 flat at the top, and perpendicular at the sides. This is 

 almost strictly true at the eastern extremity, the part 

 where its chief grandeur is displayed; but towards the 

 west it gradually becomes irregular in every respect, 

 terminating ultimately in some detached and independent 

 masses. Although it occupies the summit of a long and 

 sharp ridge of hill, it is placed more on one side of the 

 declivity than the other, in consequence of which its 

 perpendicular altitude is much greater on the southern 

 than on the northern face. The mural aspect of the 

 latter face disappears indeed entirely towards the west, 

 while on the southern the disjointed portions still preserve 

 a degree of that character to the very end. As far as 

 I could compute its length by pacing, it appeared about 

 a mile and a quarter long, the direction being from S. W. 

 to N. E. The breadth of this ridge varies with its regu- 







* Scuir, a rock. Hence the English Scar and Scaur; also skir, 

 skerries, with the compounds Hysker, Dusker, Talisker, common names 

 among the islands. See Plate V. 



