2 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 22, 



that traverse the limestone in every direction*. Eighteen years 

 later Dr. Macculloch published his 'Description of the Western 

 Islands,' wherein he pointed out the existence in Skye of secondary 

 strata — the equivalents of the lias and oolite of England, extending 

 in broken and irregular series up to what has since been determined 

 to be the equivalent of the Oxford Clayf. He also described with 

 considerable minuteness some of the more remarkable features in the 

 geology of Strath. Yet of the structure of the district he seems to 

 have had but a vague general idea — not a few of its most important 

 features having escaped his notice, while of some of the facts which 

 he mentions he has failed to perceive the true bearing. I shall even 

 have occasion to show that, notwithstanding the minuteness of his 

 description, he can only have examined a limited portion of the di- 

 strict, and that too but superficially. 



Several years later Sir Roderick Murchison examined the eastern 

 coast-line of Skye, and, from a comparison of fossils, ascertained the 

 existence and limits of strata belonging to the lias, and the lower 

 and middle oolite % ; and I am not aware that, since the date of this 

 paper, any further observations have been made upon the south- 

 eastern part of the island. 



That portion of Skye of which I offer a description to the Society 

 comprises nearly the whole of the parish of Strath. It may be re- 

 garded as an irregular belt from three to six miles in breadth, extend- 

 ing from sea to sea where the island narrows most. Its physical 

 features are those of a wide undulating valley between two elevated 

 ranges — the red sandstone and gneiss hills of Sleat to the south, and 

 the syenitic mountains of Beinn na Cailleaich and Beinn Dhearg to 

 the north. This district — embracing an area of nearly thirty square 

 miles — includes the largest development of the lias in Scotland ; and, 

 indeed, as that formation in its lower and middle divisions reaches 

 here a thickness of not less than 1500 feet, it may be regarded as no 

 unfair representative of that of England. The geological structure 

 of Strath — so intricate and confused — gives to these liassic beds an 

 additional and peculiar interest. Along the shores the strata form 

 low reefs and skerries, brown with algae, and extend in regular se- 

 quence throughout their series. Yet no sooner do they strike into 

 the interior than, in many localities, all seems to be involved in hope- 

 less confusion ; regularly stratified limestones become crystalline 

 amorphous marbles ; shales assume the appearance of metamorphic 

 clay- slate or burnt pottery ; great outbursts of syenite cut through 

 the beds, dislocating, contorting, or overspreading them ; trap- dykes 

 in countless numbers traverse the glens and the hill-sides ; while, by 

 the agency of faults, higher members of the group are thrown down 

 among the lower, and long tracts of red sandstone are brought into 

 the heart of the lias. Before attempting to detail these complicated 

 appearances, I shall describe the character and order of the beds 

 from their base upwards. 



* Jameson's ' Mineralogy of the Scottish Isles,' vol. ii. p. 91. 

 f Forbes, Quart. Journ. Geol. Soc. vol. vii. p. 104. 

 J Trans. Geol. Soc. 2nd series, pp. 293, 353. 



