﻿1851.] 



DUKE OF ARGYLL ON ARDTTJN LEAF-BEDS. 



93 



land, but having at last got on shore, we marched to the extreme 

 point or head. About a quarter of a mile from this spot is a 

 deep glen, running N.N.E. to the sea. It is about thirty yards 

 in length and twenty in breadth. The strata are disposed in the 

 following extraordinary manner. The uppermost is ten yards of 

 lava with horizontal divisions and vertical joints taking the form of 

 rude pillars. Under this is a horizontal bed of a perfectly vitrified 

 substance, which appears to have been a shale, and is from one to 

 two inches in thickness. Beneath this there is about three yards 

 of a siliceous gravelly concrete, below which are horizontal beds 

 of indurated marl of various thicknesses, from six to twelve inches. 



The whole of these beds taken together are about four yards 



Lastly, there are ten yards of rude lava, containing specks of quartz 

 and mica unaltered, pieces apparently of granite, and some nodules 

 of calcined chert. The whole is incumbent on regular basalt pillars 

 of various dimensions from eighteen to six inches in diameter." 



With the exception of the total omission of the three beds contain- 

 ing the vegetable remains, two of which, although comparatively thin, 

 are sufficiently conspicuous, this description, as will be seen, is 

 tolerably accurate. Since the visit of this gentleman, I am not aware 

 that this ravine, or "glen," the only point at which the strata are 

 sufficiently accessible to be examined in detail, has been seen or 

 known ; the neighbourhood only having been visited at different 

 times by Professor Jameson, the Marquis of Northampton, then Earl 

 of Compton*, and by Murchison and Sedgwick; and although 

 there is some ambiguity in the precise localities alluded to in some of 

 Macculloch's remarks on this district, I think it probable that he 

 had at least coasted round this headland in a boat and observed the 

 lines of stratified matter between the upper and lower basalts. 



Fig. 3. — Pictorial Section of Ardtun Head. 



1,1. Basalt, rudely columnar. 



2, 2. First leaf-bed. 



3, 3. First tuff-bed. 



4, 4. Second leaf-bed. 



5,5. Second tuff-bed. 



6, 6. Third leaf-bed. 



7, 7- Amorphous basalt. 



8, 8. Columnar basalt. 



Although aware that fossil leaves had been accidentally found a 

 few years ago in the promontory of Ardtun, I had not until this year 

 * See Trans. Geol. Soc. vol. v. Part 2. p. 369. 



