Quartzytes and Qicartz- Rocks. 187 



In connection with the Knockanteenbeg conglomerates, all 

 the inlying fragments are similar to rocks in the associated 

 underlying Kilmacrenans (probablj^ equivalents of one of the 

 sub-groups of the Algonkians of the United States, or the 

 Ontarians of Canada) yet we are asked to believe that they 

 were brought b}^ ice from districts hundreds of miles away. 

 Furthermore, our credulity is put to a still more severe test, 

 as we are asked to believe these basal conglomeratic beds to be 

 identical with the boulder-bed of the south-west and central 

 Highlands of Scotland. To this so-called boulder-bed, my 

 special attention was directed by Messrs. Home and Grant- 

 Wilson, the latter sending me specimens, and there is not one 

 iota of semblance between the two, the Scotch "boulder-bed" 

 being identical in aspect with the mullaghsawnyte of the 

 upper terrane in Co. Donegal, as was allowed by all the members 

 of the Irish staff who visited Perthshire with Mr. Grant- 

 Wilson. 



The facts that prove that the geology of the Co. Donegal is 

 still in its infancy have been so fully stated in "A New Read- 

 ing of the Donegal Rocks," that it is unnecessary to repeat 

 them, I will therefore conclude with the following remarks. 



In his prefatory" note to Explanation of Sheets 3, etc., Sir A. 

 Geikie makes a curious suggestion. Years ago, Griffith mapped 

 the rocks of the Slieve Gullion area as belonging to a much older 

 terrane than the rocks to the northward, while subsequently 

 I pointed out that these rocks to the south-west again ap- 

 peared from under the Carboniferous in the country between 

 Pettigeo and Ballyshannon. The latter conclusion was come 

 to from personal inspection and information supplied by 

 R. G. Symes. These ancient rocks formed a mountain in the 

 Carboniferous sea, and, consequentl}^, as explained in the 

 "Geology" and "Economic Geology of Ireland," the Car- 

 boniferous rocks lying on them belong to different stages in 

 that terrane. Similarly, in more ancient times, this ridge 

 was a mountain in the more ancient (Ordovician?)sea. As in 

 the Carboniferous age, so also in the much more ancient seas, 

 there may have been, or, rather there were, overlaps, the 

 lowest strata being deposited in the county to the north, while 

 the newer strata overlapped one another on the northern 

 flanks of this ancient ridge of hills. This is ocularl}' proved. 

 In the basal quartzyte of the middle terrane the fragments 

 are of the typical Donegal rocks ; but, as time went on, the 

 mullaghsawnytes of the upper terrane accumulated; they for 

 the most part being solely composed of fragments from this 

 ridge, apparently principally from the granitic rocks in the 

 Pomeroy Hills. Sir A. Geikie seems to consider he has dis- 

 covered this "core of old rocks," and, because it exists, that 

 the oldest Donegal rocks must be "on the northern flanks," 

 the evident sources of the fragments in the different accumu- 

 lations. A conspicuous character of the Irish terranes is the 



