Formation and Age of the Queensberrys. 251 



accounted for by the whole Silurian formation being thrown into 

 an extensive series of curves caused by the shrinking of the earth's 

 crust. The particular curvature exhibited at Glenkiln is known 

 as an anticlinoruni, and is accounted for by the strata being thrust 

 up into a series of ridges. The central ridge occupying the core 

 of the arch is vertical, but the smaller flexures on either side dip 

 towards the centre, and are therefore more or less inclined 

 towards the core. The crests of the folds have been eventually 

 denuded, thus destroying altogether the proper sequence of the 

 formation. The Glenkiln shales and cherts form the centre of 

 this composite fold with the Hartfell shales occupying one of the 

 troughs or synclines. The dip of the trough is towards the 

 centre of the disturbance, thus giving the whole group an in- 

 verted appearance. Finally, great masses of rock were removed, 

 laying bare the central core of cherts and volcanic lava. 



The Pishnack Burn further north affords another interesting 

 section. This burn, along with the Bran Burn, flows from the 

 Wee Queensberry into the JE. About 300 yards above their 

 junction the Pishnack flows past a prominent cliff on its left bank. 

 Further up stream there is an outcrop of black shales, which from 

 the character of the rock and the nature of the fossils are un- 

 doubtedly the same group of Hartfell shales previously described. 

 On this occasion, however, they occupy the centre of the arch, 

 thus leaving the strata on either side to fill up the minor folds. 

 Immediately overlying the Hartfell shales is a large mass of grey- 

 wacke, known as the Barren mudstones. As its name implies, 

 it is devoid of fossils, with the exception of a thin band of shale 

 at the foot of the mudstones and another near the top. The 

 graptolites in these indicate different life zones, and are known as 

 the Upper Hartfell group. 



Descending the stream, another outcrop of shales is encoun- 

 tered, known as the Birkhill group. In appearance they are 

 quite distinct from the other groups already described. The 

 shales are more fissile, and contain white seams and bands of 

 clay. The great difference, however, is found in the fossils. 

 They declare an absolute change. All the previous forms of life 

 are found to be extinct except three genera. The abundance of 

 a liew genus, Monograptus, marks the dawn of a new era, 

 described as Upper Silurian. The various species of Mono- 

 graptus show the highest possible development of the whole 



