NICOL SOTJTHEEN GEAMPIANS. 



195 



preponderance of dips to the south, but nearly balanced by dips to 

 the north. The dips are frequently at low angles ; and, on the whole, 

 I have no doubt that on the north side of Loch Earn the mica-slate 

 forms a marked anticlinal axis, probably the continuation of the axis 

 of highly contorted beds noted above on Loch Long, Loch Lomond, 

 and Loch Lubnaig. The limestone, formerly quarried on the upper 

 part of Loch Earn, appears to lie deep in this series, and is probably 

 overlain by the greater part of the mica-slate, both higher and lower 

 on the loch. This limestone is large-grained, crystalline, and of a 

 grey, or rather mixed white and black colour. It is wholly unlike 

 the Leny limestone near Callander, but closely resembles some of the 

 limestones in the mica-slate of Cantyre. The limestone is also wrought 

 at Edinample, on the south side of Loch Earn, and also runs N.N.E. 

 for some miles up Glen Yech. The dip, generally at low angles, 

 varies, however, even in the main quarry, from N. 57° W. to 

 S. 67° W. The limestone seen on the south side of Loch Tay, also 

 in the mica-slate, is probably the continuation of this deposit, whilst 

 the beds on the north side of that lake, dipping below Ben Lawers, 

 are the same series brought up by a fault*. This view is repre- 

 sented in the diagram, fig. 8. 



n. 



Eig. 8. — Section from Loch Earn to Loch Tay. 



Loch Tay. Loch Earn. 



a. Limestone. 



Trap. 



As already stated, the relation of the clay-slate to the mica-slate 

 is not clearly exhibited in any single section. At the foot of Loch 

 Earn, near St. Fillans, the clay-slate and greywacke have a very 

 constant dip W. 32° S., and consequently a strike N. 32° W. This, 

 as formerly noted, is the general direction of the stratification in the 

 slates, and nearly at right angles to the direction just deduced for 

 the mica-slate (E. 22° N. or, better, E. 40° N".). This strike of the 

 mica-slate more nearly corresponds with the strike of the other set 

 of planes, or the foliation of the clay-slate, which we found E. 10° N., 

 but still deviates from it, on what I consider the better determina- 

 tion, by 30°. Besides, whilst the dip of the mica-slate is predomi- 

 nantly to the south, that of the clay-slates is very constantly to the 

 north. We must therefore conclude that in Strath Earn the mica- 



* In my Guide to the Geology of Scotland, p. 170, 1 stated that " Loch Tay lies 

 in a valley of elevation ;" and Sir R. I. Murchison says that it " lies on an anticlinal 

 fold" (Note to New Sketch-map, p. 17). In the section on my Geological Map 

 of Scotland, the strata on both sides of the loch are represented as dipping N.W. 

 This is the result of my observations round Killin, where that section crosses the 

 valley of Loch Tay. 



o2 



