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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Dec. 5, 



slightly undulating beds. On the east side of this hill the limestone 

 rests on the red shales or fucoid-beds (c 2 ), and these in turn on the 

 quartzite (c 1 ), dipping at 20°, to W. 40° 1ST., and rising in great curved 

 beds to the top of the next hill. The section is so clear, and the 

 correspondence of the deposits so exact, that there can be no doubt 

 that this is the east side of the Queenaig synclinal. Still stronger 

 evidence of this fact may be obtained by tracing the quartzite along 

 the shore of Loch Assynt and up the Stronchrubie valley*, every- 

 where dipping below the limestone, till it turns round its southern 

 extremity and rises up into Brebag. From this mountain the 

 quartzite may be followed along the bare ledges of rock north to 

 Ben More, and thence, as shown in the section, round till it again 

 joins that of Queenaig. 



A more interesting confirmation of this peculiar structure of the 

 Assynt district (the highest of its formations, filling the bottom of 

 the valley) is furnished by the drainage of its waters. Almost all 

 the streams from the lofty north-eastern mountains, from Brebag, 

 Ben More, and Ben Uarran, on reaching the synclinal line in the 

 limestone, fall into swallow-holes and disappear for a considerable 

 space. The whole moor is dotted over with round pits, some dry, 

 some filled with water at the bottom, through which the drainage is 

 effected. In some places deserted river-beds, only occupied by the 

 water in rainy seasons, are seen ; in other places the subterranean 

 torrent is heard rolling along at the bottom of a deep dark cave. 

 Now all this underground drainage is directed towards Loch Assynt, 

 the centre of the synclinal, proving that the strata dip to this point, 

 and not north or east below Ben More or Brebag. The water de- 

 scends through the limestone to the quartzite, and is again thrown 

 out on the surface by this impervious stratum, often in very copious 

 springs f. 



There is thus, in this place, no " upper quartz-roek " resting on 

 the Stronchrubie and Assynt limestone, and the hills referred to this 

 newer formation clearly consist of the quartzite below the limestone, 

 brought up over an anticlinal. Singularly enough, too, some of 

 these so-called " upper " or " newer quartz-rocks " are even an older 

 formation than the lower quartzite. When examining Canisp and 

 Queenaig, I was struck by the peculiar aspect of some of the hills on 

 the eastern side of Stronchrubie, usually classed as quartzite. From 

 their reddish colour I thought that they probably consisted of felspar- 

 porphyry, like that of Loch Borrolan ; but on examination I found 

 that they were formed of red sandstone, identical in character with 



* In my former paper (Quart. Journ. Geol. Soc. vol. xiii. p. 25) I stated that 

 the Stronchrubie limestone and the underlying quartzite had "probably been 

 brought up by a fault." Several faults in the line of that section are well seen 

 in the face of the Stronchrubie cliff; but, as shown in the present section, the 

 limestone and quartzite are brought up rather by undulations in the beds and 

 the general rise of the synclinal than by these faults. Compare Quart. Journ. 

 Geol. Soc. vol. xvi. p. 221 (note J). 



t I estimated the flow of the "Eemarkable Spring" above Stronchrubie at 

 7000 gallons per minute, after some weeks of dry weather. 



