408 C. CALLAWAY ON THE NEWER GNEISSIC 



The significance of these facts is obvions. As the quartzite in 

 these outliers rests unconforrnably upon the Caledonian, the latter 

 must be the older series. 



Prof. Mcol, whose identification of the gneiss as "intrusive 

 granulite " precluded him from the use of this argument, described 

 what he considered an outlier of the younger rocks at Cnoc Craggie, 

 near Tongue. With his interpretation I am unable to agree. The 

 hill is a mass of breccia, the fragments being chiefly composed of 

 the flaggy gneiss. The rock bears no resemblance to the Torridon 

 Sandstone, to which Nicol referred it. The quartzite, which he 

 supposed to overlie at the southern end, refused to disclose itself, 

 though I searched every yard of the ground. The only stratified 

 rock visible was the ordinary thin-bedded gneiss, which towards 

 the hill became hrecciated and appeared to pass into the breccia. 

 A reddish granite is intruded at this point. 



E. Granite not intrusive in the Assynt Series. 



If the gneiss normally overlies the Assynt rocks, we ought some- 

 times to find granite intrusive in the latter. Yet although the gneiss 

 in the Erriboll area is, as Murchison stated, " riddled" with granite, 

 the granite never appears in the adjoining quartzite. Murchison, 

 indeed, describes what he considered an example of such intrusion 

 in the north-and-south ridge east of Heilem *. My examination of 

 the rocks did not lead to the same conclusion. In the centre of the 

 ridge, I found not only granite but a narrow wedge of gneiss, which 

 certainly could not be intrusive in the ordiuary sense. I observed, 

 moreover, that the quartzite, flags, and dolomite on each side were 

 tilted up by the interior mass, whereas the granite in the gneiss of 

 this area does not produce this effect. On the east side, dolomite 

 dipped away at a moderate angle ; and on the west, the flags, which 

 in one place dipped away from the ridge at 80°, were seen, when 

 traced down the steep slope, to rise to the vertical, and then to fall 

 over to the west, so as to dip into the hill. The so-called " intru- 

 sive granite " is, then, a linear wedge of gneiss with granite in it, 

 thrust up amongst the overlying Assynt series, which, on the west 

 side, it actually overthrows. The ridge is precisely on the geogra- 

 phical strike of Druim-an-tenigh, and the overthrow is similar. 



III. Igneous Rocks. 



The result of my work has been to considerably reduce the quan- 

 tity of igneous rock supposed to exist in the North-western High- 

 lands. Omitting ordinary dykes and small masses of dolerite and 

 felsite, the following deserve notice. 



* Called " Drunitungi " in his section (Quart. Journ. Geol. Soc. 1859, vol. xv. 

 p. 234). This name, or "Druim-an-tenigh," is, however, given to the ridge 

 lying to the south, described by me above. 



