NEWER GNEISSIC EOCKS OF TEE NORTHERN HIGHLANDS. 355 



22. The Age of the newer Gneissic Rocks of the Northern High- 

 lands. By C. Callaway, Esq., D.Sc, M.A., F.G.S. With 

 Notes on the Lithologt, by Prof. T. G. Bonnet, M.A., F.R.S., 

 Sec. G.S. (Eead May 9, 1883.) 



Contents. 

 Introduction. 

 I. The Formations concerned in the result (p. 357). 



a. 



Hebridean. 







b. 



Caledonian. 







c. 



Assynt series. 



1. Probable age. 



2. Subdivisions. 









c v Torridon Sandstone and Ben More Grit. 





c 2 . Quartzite. 









c 2 1. Seamy. 



c 2 u. 



Annehdian. 





c y Brown flags. 









c 4 . Scdterella- grit 



and quartzite. 







c 5 . Dolomite. 









c s I. Dark. 



c 5 ic. 



White. 



II. The Eelations between these formations (p. 363). 

 Loch Broom (p. 363). 



1. Section along the shore of the loch, from Ullapool to the S.S.E. 



2. Section along the road, from Ullapool to the S.E. 



3. Section from Ullapool to the E.S.E. 



4. Section from Ullapool over the high ground to the E.N.E. 



5. Section along the south side of the Ullapool river, W. to E. 



6. Section along the north side of the same, W. to E. 



Assynt (p. 367). 

 A. The "Upper" Quartzite non-existent (p. 367). 

 Section on the Burn of Calda. 

 Scarp between Calda Burn and Poulan-drein. 

 Section on Poulan-drein. 

 Quartzite of Cnoc-an -drein. 

 " Logan Bock " of Glasven. 

 Section from the west end of Ben Uarran to the high road south of 



Incbnadamff. 

 Section in the Balloch under Coniveall. 

 Section up Glen Coul. 



b. The " Logan Bock " not separable from the Hebridean (p. 374). 



{a) Objections to the Hebridean age of the " Logan Bock " considered. 



(1) Absence of accessory miuerals in the " Logan Bock." 



(2) Absence of bedding in the same. 



(3) Foliation in the "Logan Bock" not coincident with bedding. 



(4) Difference of weathering. 



(6) Author's objections to the contemporaneity of the " Logan Bock " 

 with the Assynt series. 



(1) The " Logan Bock " not conformable to the rocks below it. 



(2) Or to the rocks above it. 



(3) The strata below it not metamorphosed. 



(4) No beds of passage between it and the rocks above and below. 



(5) Alteration and crushing at its junctions with other rocks. 



(6) Strikes of the "Logan Bock" and Hebridean often concordant. 



