198 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. 



the older. It seems a ready solution of the difficulty to declare both 

 formations identical, and to affirm that there is no normal order or 

 arrangement in them. This, however, is a mere evasion, not a solu- 

 tion, of the question. The mica-slate and clay-slate are too distinct 

 to be thus conjoined ; and Dr. Macculloch, who first pointed out (more 

 strongly, I suspect, than facts will warrant) their alternations and 

 transitions, fully admits their claims to be considered distinct geo- 

 logical formations. Besides, the difficulty, evaded in words, really 

 recurs in another form. How is it that the more metamorphic 

 portion of the series, which is lowest in one place, is highest in the 

 other ? Still more, the bed of clay-slate is known and quarried at 

 so many points along the line from Bute to Stonehaven, that its 

 physical continuity can scarcely be doubted ; and the question recurs, 

 how is it that this bed, which in the west forms the highest part of 

 the series, appears in the east as the lowest ? 



In further considering this curious phenomenon, the first point 

 for inquiry is, what is the normal order of the two formations ? Is 

 the clay- slate regularly the upper or the lower deposit ? The analogy 

 of other localities leads us to believe that the clay-slate is the higher 

 and newer formation ; and the lower inclination and more regular 

 dip of the beds in Bute and on the Gareloch confirm the view that 

 the strata there are in their normal position. The reversed position, 

 therefore, seen at Callander and other points to the north-east must 

 be abnormal. We thus again return to the second question, How 

 has this peculiar position of the clay- slate been effected? Now I am 

 inclined to regard this infraposition of the clay-slate as, in part, only 

 apparent. Besides the great fault intervening between the red 

 sandstone and the clay-slate, other faults, approximately parallel to 

 it, run through the clay- slate, along which the dykes of trap and 

 other igneous rocks have found their way to the surface. The pri- 

 mary strata have thus been divided into longitudinal sections, and 

 each section having been tilted up from the south, the rocks all 

 dip north, towards, and apparently under, the centre of the chain. 

 But at other places, and especially at Callander, a real infraposition 

 of a portion of the clay-slate takes place, caused I believe by a com- 

 plete folding over or reversal of the beds. The first portion of the 

 strata in the Pass of Leny has been raised up from the south, and 

 dips normally to the north-west. Near the foot of Loch Lubnaig 

 there is a fault, and immediately beyond it the whole strata have 

 been folded over, so that the clay-slate comes to dip under, or rather 

 to be folded up in, the mica-slate. This change has taken place in 

 the country to the south-west, and, it would appear, in a gradual 

 manner, the strata rising from a dip of 40° or 50° on the Gareloch 

 to 80° or 90° on Loch Lomond, and at Callander being turned com- 

 pletely over to the south. 



There are two subsidiary facts supporting this view of these re- 

 lations. First, the highly inclined position of the conglomerate and 

 red sandstone proves, as stated above, that they have been acted on 

 by a force from the north-west, not merely raising up the beds, but 

 pushing them in a south-east direction, — that is, such a force as the 



