aABBROS ETC. IN SCOTLAND AND IRELAND. 57 



date. It may be regarded as intruded trap, insinuated between 

 superior and inferior strata at an epoch long posterior to that of the 

 deposition of the former. A minuter investigation of the geological 

 phenomena of the north and west of Skye than has yet been made 

 will probably determine which view is the right one beyond ques- 

 tion. But in the present state of the evidence, I incline to regard 

 the basalt as contemporaneous with the Oolites, and as of the definite 

 date which its position in sequence of beds seems to indicate " *. 



In 1860, Dr. A. Geikie adopted the suggestion of Forbes with 

 respect to the Jurassic age of a portion of the volcanic rocks of the 

 West of Scotland f ; but he also guarded himself, as Forbes had done 

 before him, and admitted that there was doubt whether the igneous 

 masses associated with the Oolites are not intrusive rather than 

 interbedded. 



But in 1867 J, Dr. A. Geikie fully withdrew this suggestion as to 

 the Jurassic age of the Hebridean igneous rocks, so far as Mull and 

 the adjoining islands were concerned, and in this and subsequent pub- 

 lications §, returned to the views which had always been maintained 

 by Macculloch, namely, that the whole of the igneous masses are of 

 later date than the Secondary strata, and that, wherever associated 

 intimately with these latter, they constitute intrusive sheets and 

 dykes. He also added some interesting observations in support of 

 the view that these igneous rocks are of Tertiary age, the chief 

 among .them being that there exist river-gravels made up of chalk- 

 flints interbedded with the basalts at Carsaig in Mull. 



Now it is a most unfortunate circumstance that some continental 

 geologists have adopted the suggestion of the late Professor E. Forbes, 

 and of Dr. A. Geikie, without noticing their reservations ; while they 

 appear to have altogether overlooked the fact of the complete aban- 

 donment of the hypothesis of the Jurassic age of these igneous 

 rocks by the latter author. 



In 1871, Dr. Zirkel published his '• Geological Sketches of the 

 West Coast of Scotland," in which he gives a section of Trotternish, 

 in Skye, based on the erroneous one of Edward Forbes || ; he does 

 not appear to have been acquainted with the earlier and correct 

 views enunciated by Macculloch, nor of the acceptance of those 

 views in the end by Dr. A. Geikie. This misleading section has 

 unfortunately been copied into the different editions of Dr. Credner's 

 admirable and widely known 'Elemente der Geologic,' and its French 

 translation. 



During my own survey of the Secondary rocks of the west 

 coast of Scotland, I was able to show that not only are Jurassic 

 rocks represented in that area, but that we find important deposits 



* Loc. cit. p. 109. 



t Trans. Eoy. Soc. Ediub. vol. xxii. ; see also ' Scenery and Geology of 

 Scotland ' (1865). 



\ Proc. Eoy. Soc. Edinb. vol. vi. pp. 71-75. 



§ Brit. Assoc. Eep. 1867. Address to Geological Section, p. 52- Quart. 

 Journ. Geol. Soc. vol. xxvii. (1871) pp. 279-310. 



II Zeitscbr. d. d. Geol. Gesell. vol. xxiii. (1871), Taf. iv. f. 13. 



