Geological Society. 455 



during the last summer, the districts which he described in a former 

 memoir, (Geol. Trans. 2nd series, vol. ii. part 2.) has been enabled to 

 make some additional observations, and to collect further specimens 

 illustrative of the strata of the oolitic series, and their associated rocks 

 in the north of Scotland. 



1. On the connection of the primary rocks with the secondary 

 doposits on the east coasts of Sutherland and Ross. — The Ord of 

 Caithness, and the mountainous ridge connected with it, which had 

 been described as consisting of a rock made up of felspar, quartz, and 

 a decomposing green substance, is now ascertained to contain well- 

 crystallized mica. This granite, on its northern flank, supports the 

 old red conglomerate ; whilst to the south it occupies a cliff on and 

 near the shore, the verge of which affords a remarkable breccia, com- 

 pounded from all the beds of the oolitic series which occur upon this 

 coast. These appearances were cursorily noticed in the author's paper 

 above referred to ; they are now described more in detail : and it is 

 shown, that this breccia of sandstone shale, fossils and limestone, is 

 tilted off from the granite, wherever that rock ])rotrudes upon the 

 shore ; whilst the strata are regularly developed when the granite 

 recedes into the interior : — and since the amount of disturbance is in 

 every case proportioned to the greater or less proximity of the granite, 

 the author infers, that this rock was elevated subsequently to the de- 

 position of the oolitic strata. Thin beds of primary slaty rocks have 

 been observed in several places, interposed between the secondary 

 beds and the granite : and the greater portion of the Sutors of Cro- 

 marty consist of felspathose gneiss ; which rock, however, is in some 

 .situations so much cliarged with veins of granite, that the whole has a 

 granitiform aspect, whilst in other places the mass when decomposed 

 strongly resembles the rock of the Ord of Caithness above mentioned. 



That the granite of this coast has been elevated, is further rendered 

 fwobable, by the position of the red conglomerate on the tops of the 

 granitic mountains ; thus giving to that deposit the appearance of 

 overlying the more recent formations of the oolitic series, to which 

 they are in fact superior in point of height above the sea. 



Without dissenting from the opinions of other geologists, as to the 

 formation of veins in gneiss by the injection of granite in a state of 

 softness, the author states that Mr. Sedgwick and himself were led 

 to a different hypothesis, in order to account for the ap])earance of 

 the brecciated secondary beds in contact with the granite of this coast : 

 and they suppose that the latter rock must have been upheaved, not 

 in a liquid form, but in a state of solidity, since no veins or portions 

 of the granite are to be met with in or above the breccia. 



2. Denudation of Braambury, and Hare Hills — These hills, the 

 highest in geological ])osition of the Brora district, and celebrated 

 for their quarries of siliceous white sandstone abounding in fossils, 

 afford, upon tlieir sides and summits, distinct traces of a strong dilu- 

 vial current, which lias swept them free of covering matter, depositing 

 in the plain of ('lync Miiltown, a mass composed of the debris of the de- 

 nuded hills, mixed with boulders of the coarse red conglomerate. A 



iiirgc 



