1858.] MTIRCHISON— NOETHERN HIGHXANDS, ETC. 397 



inclines to the N.E. at about 10°, and soon graduates up into pui'plish 

 and grey siliceous and micaceous thin-bedded sandstones, covered by 

 the true dark-grey (in parts almost bluish) flagstones, which, after 

 curvatures (doubtless accompanied by breaks vs^hich are hidden by 

 moss), become highly fossiliferous in the adjacent hills of Bannis- 

 kirk, &c. 



Fig. 11. — Section showing the Melations of the Lower Members of the 

 Old Bed Series near Dirlet Castle. 



Dirlet 

 Castle. 



* Gneissic and flaggy schists, penetrated by granite, a. Grranitle conglomerate, or 

 lowest member of the Old Red Series, b. Sandstone, c. Caithness flagstones. 



In following the Old Red conglomerate southwards along the east- 

 ern part of Sutherland, where it forms the inland boundary of the 

 coast-range of the Oolitic beds of Helmsdale, Clyne, and Brora, which 

 it separates from the crystalline rocks, the mass may much more 

 truly be called a breccia ; for here the included fragments, which are 

 lodged in a paste of pink-coloured or granitic sand, are micaceous 

 fragments of all the varieties of the quartz-rock series, viz. hard, 

 micaceous, finely laminated sandstones of various colours passing on 

 the one hand into gneiss, and on the other into pure quartz-rock. 



On the south flanks of Wyvis, the loftiest mountain of Eoss- shire, 

 the gneissose flagstones are truncated, and flanked by enormous masses 

 of conglomerate and sandstone, in which are deep rents wherein the 

 streams descend to the Bay of Cromarty. One of the most remark- 

 able of these gorges is watered by the Alt Grant, the massive con- 

 glomerate precipices on the sides of which have been described by 

 Sedgwick and myself* ; another is that in which the Alness River 

 flows. In ascending that stream above the House of Ardross, the 

 formation is perceived to assume an aspect differing a good deal from 

 its usual appearance. In their upper parts the beds are of dark- 

 grey, greenish, and deep -red soft shale, either highly inclined or 

 in rapid undulations, and in the lower part of a veiy coarse conglo- 

 merate and a reddish and yellowish, gritty, thin-bedded sandstone. 

 The lower portion of the conglomerate is here not only vertical and 

 much twisted, but is also much mineralized and contains a thick vein 

 of rich hematitic iron-ore. All these lower beds of the Old Red 

 have been deposited quite athwart the edges of the quartzose flag- 

 stones and mica-schist of "Wyvis and its adjacent mountains, which 

 have the usual dominant strike of N.N.E. or JST.E. and S.W., whilst 

 the conglomerate and sandstone of this tract strike nearly east and 

 west, and dip southerly at angles decreasing as you recede from the 

 mountains. 



Allusion was formerly made to the bold forms which the Old Red 



* Trans. Geol. Soc, Lond. 2nd ser. vol. iii. p. 147. 



