ROCKS OF THE NORTHERN HIGHLANDS. 379 



the Assynt series ; and for the purpose of this paper it is immaterial 

 to which they belong. The majority of the above-named specimens 

 are undoubted gneiss, taken from the " Logan Rock " near its 

 faulted junction with other rocks. 



6. Strikes of the " Logan Rode " and Hebridean frequently con- 

 cordant. — It is usually affirmed that the prevailing strike of the 

 Hebridean is north-westerly. This holds for some districts, but it 

 only partially applies to Assynt. On the south side of Loch Assynt 

 the strike is E.N.E. ; and on the north side, where we first come 

 upon it after leaving the Torridon, the strike is 2ST. 10° W. Further 

 to the north, on Loch Glen Coul and the slopes south of Kyle Sku 

 ferry, the dip is to the N.'W. at low angles ; but, leaving the north 

 side of the ferry, and following the path to the N.E., which leads 

 to Loch More, the strikes are seen to vary frequently, my note-book 

 furnishing the following changes, taking the strikes from west to 

 east— viz. E. and W., W.N.W., W.S.W., ft. and S., N.W., W.S.W., 

 W.jNT.W., and N.N.W., the prevailing direction perhaps being north- 

 westerly. Taking the Hebridean of Assynt as a whole, the varia- 

 tions are too great to permit a general induction. 



Coming to the " Logan Bock," we have seen that its usual strike 

 in the central masses of Ben More is N.N.E. or N". 10° E. In 

 Glasven the foliation is to the N.N.W., concordant with the strike 

 of the nearest Hebridean (on Loch Assynt). In Glen Coul the 

 strike is N.W. ; and in Glen Dhu, E. and W. — tbat is, more or less 

 transverse to the strike of the undisturbed Hebridean under the 

 Quartzite on Loch Glen Coul, but agreeing more nearly with the 

 prevailing strikes on the road to Loch More ; indeed the strike of 

 the " Logan " of Glen Coul, if produced to the N.W., would coincide 

 with that of the admitted Hebridean on the Loch More road. 



Comparing the "Logan Bock" as a whole with the Hebridean 

 as a whole, the coincidences of dip and strike are greater. Thus, in 

 the northern part of Assynt — that is, in Ben Uarran and Glasven, 

 and between Lochs Assynt and More — the " Logan Eock " strikes 

 westerly or north-westerly, as in typical Hebridean ; and in the 

 Ben More masses, though the strikes vary between a few degrees 

 E. or W. of N., the dips are very high, frequently nearly or quite 

 vertical, as is so frequently the case with the old gneiss. 



C. Direct Proof of the Overthrow of the Hebridean. 



Many of the considerations already advanced point to the con- 

 clusion that the " Logan Eock " is the Hebridean gneiss brought up 

 over the Assynt series by earth-movements. But evidence still 

 more decisive can be adduced. 



We have seen that the vertical or high-dipping gneiss of Ben 

 More is overlain by horizontal conglomerate and grit (No. 94, 

 p. 417), forming the base of the " Upper " Quartzite. The place 

 of the Ben More Grit is then above the gneiss (Logan Eock). In 

 the ground to the south this relation is reversed. 



