Yol. 62.] THE CRAG OF ICELAND. 713 



than the Eed Crag, while, on the other hand, a consideration of the 

 number of Arctic forms makes us believe that perhaps the palaeonto- 

 iogical evidence of Tjornes may lead up to the opening scenes of 

 the Pleistocene. 



As to the position of the Crag in the Icelandic rock-succession, 

 Prof. Th. Thoroddsen thinks that the Pliocene beds are of later 

 date than the eastern higher part of Tjornes, which, according to 

 that author, constitutes a projecting remnant of the old basalts 

 ('horst ') against which the Pliocene strata are resting. 1 According 

 to Prof. Thoroddsen, the Icelandic Crag ' points to a level of the sea 

 some 150 or 200 feet higher than the existing level.' 2 



The Crag-formation extends along the western coast of Tjornes 

 for more than 3 miles, forming a fine cliff up to 200 feet in height. 



A glance at a topographical map of Iceland will at once show, by 

 the existence of a comparatively-broad bay, what part of the Tjornes 

 •coast is built up by the Pliocene deposits. 3 



It is not my intention here to enter upon a description of the 

 Icelandic Crag, but only to mention a cardinal fact concerning it 

 which has been too long overlooked. Following the Pliocene beds 

 away from the coast up along the stream-courses, we find that, at a 

 height of about 500 feet above the sea, they are over- 

 Iain by the eastern basalts. The superposition of the basalts 

 upon the fossiliferous series is very clearly seen, and at the contact 

 the underlying sediments are indurated and otherwise altered. 

 AYe thus find that, far from resting against an older Tertiary ' horst,' 

 the Crag of Tjornes is older than the eastern basalts, which in 

 Burfell — part of a denuded Pleistocene volcano — attain a height of 

 2500 feet. 4 



The Crag of Iceland, then, is a fossiliferous intercalation — 

 exceeding in thickness 500 feet — in the basalt-formation, or rather 

 between the two basalt-formations of Iceland, the Tertiary and the 

 PJeistocene, which are separated by a great gap. Harmonizing 

 with this, we find intercalated among the eastern basalts of Tjornes 

 indurated ground-moraines with striated stones. 



As the majority of naturalists who have visited Iceland have 

 examined the Crag of Tjornes, it may seem almost incredible that the 

 above-mentioned most importaut fact for the geology of the country 

 should have remained so long undiscovered. This is, however, 

 easily understood ; no one ever doubted the Tertiary age of the 

 rocks that build up the eastern, higher part of Tjornes ; and so 

 investigators spent all the time at their disposal in studying the fine 

 sea-cliff — as, indeed, was the case with myself, on my first visit to 

 Tjornes. 



1 ' Islandske Fjorde og Bugter' Geograf. Tidsskr. vol. xvi (1901) p. 67. 



2 ' Explorations in Iceland, etc' Olograph. Journ. vol. xiii (1899) p. 34 

 sep. cop. 



3 [This has not, however, been remarked by Prof. Thoroddsen, whose map 

 gives a very incorrect idea of the area occupied by the Crag.] 



4 See H. PjetursBon, 'Oin Islands Geologi ' Copenhagen, 1905, p. 44. 



3c2 



