392 TF. II. Hudleston — First I/iipressions ofAss//iit. 



rubie, to Craig-a-Knockan, opposite Coiil More. It is true that near 

 Ledbeg, along tliis line of road, there is some deviation from the 

 normal state of affairs, but the fact of there being " Logan " rock 

 exposed in the vicinity is quite enough to account for the deviation, 

 as, wherever there is '■' Logan " rock, trouble is sure to ensue. 



So far, then, the geological sequence is tolerably clear. This 

 Quartzite has intercalated bands of igneous rock, and dips regularly 

 towards the longitudinal hollow which separates the western from 

 the eastern range. There can be little doubt that the hybrid group 

 of rocks known as the " Fucoid Beds " succeed in regular order. 

 These beds are mixtures — chiefly fine-grained grits often with a 

 considerable proportion of carbonates, usually blue-hearted, and 

 weathering yellow : hence the term " yellow beds " is applicable on 

 exposed outcrops. As there is so little alteration, these are just the 

 beds for fossils, but only "Fucoids " and "Serpulites "^ have as yet 

 been found. The former are very abundant. Beds of tolerably 

 pure quartzite, and even of dolomite, occur sometimes in this group. 

 Such qnartzites, however, have nothing to do with the supposed 

 Upper Quartzite, whose position, if it exists at all, must be above the 

 main mass of Dolomite, which succeeds the "intermediate" series. 



These dolomites generally occupy the escarpments which imme- 

 diately flank the east side of the longitudinal hollow, and may be 

 well studied, among other places, in the Stronchrubie cliff, which 

 rises about 450 feet above the road. The lowest beds there seen 

 are dusky dolomitic rocks, granular or compact, and very foetid. 

 They contain noticeable traces of carbonaceous matter, and are 

 tolerably free from insoluble rock debris, at least the sediments are 

 very fine. At this place a kind of diorite is seen to be interbedded 

 with these dusky rocks, which are succeeded by grey dolomitic 

 limestones, becoming paler in colour towards the top. Up to this 

 point everything seems clear and simple ; yet a thorough examina- 

 tion of this Quartzite-dolomite group, with accurate measurements 

 and careful lithological notes, especially with reference to the num- 

 ber and nature of the bedded " igneous " rocks, would be very useful. 

 It may not be practicable to get the whole group in one section, but 

 suitable places might be selected for examination of portions, avoid- 

 ing as much as possible places where a hollow covered with vegetation 

 intervenes, and above all, in putting the pieces together, nothing 

 should be taken for granted. 



Very shortly after reaching the edge of the plateau, the dolomitic 

 limestones are seen dipping at a very high angle, and further east- 

 ward they dip in a very different, though not exactly opposite 

 direction. A certain amount of these very irregular dips may be 

 due to percolation of water and unequal solution, yet much also is 

 due to the general stratigraphical confusion which here begins to 

 prevail — a prelude to the still more terrible confusion of the eastern 

 range whose roots we are now approaching. 



^ From an examination of two hand-specimens of a white grit, or quartzite, full of 

 the so-called " Serpulites ? llaecuUochii,'^ Salter (see Quart. Journ. Geol. Soc. 1858, 

 p. 381, pi. 13, fig. 31), I venture to think that their appearance is highly sugges- 

 tive of crinoidal fragments. — Edit. Geol. Mag. 



