Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/550

 those of Sutherlandshire and Assyut. If this were the case the nomenclature of the Geological Survey would have to be altered, and the rocks of Pistyl and Holyhead no longer termed metamorphosed Cambrian rocks, but Laurentian.

Mr. Hicks, in reply, stated that the quartziferous breccias forming the central ridge contained so many rolled pebbles, and were, moreover, in places so distinctly bedded, that there could be no doubt of their being sedimentary. Other beds, described as Greenstone in the maps of the Geological Survey, were also distinctly laminated. The non-occurrence of fossils in the more sandy beds he attributed to their having been deposited in very shallow water. The fossils occurred principally in fine-grained beds of a flaggy nature.

2. On the Age of the Nubian Sandstone. By Ralph Tate, Esq., Assoc. Linn. Soc, F.G.S.

Mr. Bauerman, in a recent number of the Quarterly Journal of this Society (vol. xxv. p. 27), has discussed at some length the opinions advanced respecting the age of the sandstone strata underlying the Cretaceous limestones, and resting upon the granitic and schistose rocks, in Sinai. These rocks belong to the same series of sandstones described by Russegger as occurring in Egypt, Nubia, and Arabia Petraea, under the name of " Nubian Sandstone."

Though the facts that I have the honour to submit to the Society may be stated in a few words, yet it seems desirable to recapitulate briefly the views that have been advanced as to the period of deposition of the strata in question, the better to explain away those inferences which are so much at variance with my own.

In the first place, it appears, from the circumstance of the Nubian Sandstone being overlain conformably by approximately horizontal strata of Cretaceous age, that this formation has been regarded, in the absence of palaeontological evidence to the contrary, as forming part of the Mesozoic group of rocks. Thus Russegger colours and describes it as Lower Cretaceous in his maps ; and Bauerman, guided by the lithological similarity of its strata to the Lower New Red Sandstone about Chester, has placed it on the horizon of the Trias ; whilst Figari Bey seems to have regarded the tripartite arrangement and lithological features of the series as sufficient tests by which to assign the whole to the Trias, " taking the limestone as representing the Muschelkalk, although the evidence for this determination (other than lithological character) is not very clear "*.

In the second place, the fossils which have been obtained from the limestone separating the sandstone into two great masses are, for the most part, fragmentary, in bad condition, or otherwise undeterminable. Hence the palaeontological evidence is of a most con-


 * Bauerman, loc. cit. p. 27.