Correspondence — Mr. Henry Sicks. 47 



Galway the geological age of tlie rocks is quite plain to those who 

 will take the trouble to carefully work them out in detail ; some of 

 these rocks are excessively metamorphosed, in places being altered 

 into granite, yet these granites can be traced into gneiss, and from 

 that through schist and the " submetamorphic rocks " into rocks 

 that contain fossils similar, according to Baily, to those character- 

 istic of the Llandeilo rocks. Yet now we are told that the extremely 

 metamorphosed portion of these rocks " are probably of Laurentian 

 age." In one of the papers previously referred to. Sir E. I. 

 Murchison made a somewhat similar statement, but in a subsequent 

 paper he retracted it. 



G. H. KiNAHAN. 

 OvocA, Dee. 8th, 1881. 



"MONTALBAN" EOCKS IN SCOTLAND. 



Sib, — In the published account of the verj'- interesting and 

 important address delivered before the Geological Society on Nov. 

 16th, by Dr. Sterry Hunt, '• On the Eozoic Eocks of Europe as com- 

 pared with those of North America," it is stated that the " Pebidian 

 of Hicks includes both the Huronian and the Montalban, to which 

 latter belong, according to the speaker, certain gneisses and mica- 

 schists both in Scotland and Ireland." I have repeatedly expressed 

 the opinion that the great Pebidian formation, as at present defined 

 in this country, will have to be divided into several distinct series, 

 and that it is not improbable that we include in it now formations 

 unconformable to one another. In describing the Scotch rocks 

 (Proc. Geologists' Assoc, vol. vii. p. 20), I called special attention to 

 a series of gneisses and mica-schists along the sides of Loch Eil, and 

 I said that these " differ considerably from those further west, and 

 strike from N.E. to S.AV., with an average dip of about 45° to the 

 N.W. They alternate with a corrugated mica-schist and with 

 quartzose bands, which are spotted with a greenish micaceous 

 mineral. These I look upon as newer than the Loch Shiel series, 

 and probably faulted down against the latter. Thej^ should probably 

 be classed witlx the Pebidian rocks of Anglesea, and with others to 

 be further referred to in the more central parts of Scotland." I 

 showed specimens of these rocks to Dr. Hunt, and he immediately 

 recognized their great resemblance to his Montalban series. My 

 chief reason for including these in the Pebidian was that they are 

 undoubtedly newer than the gneisses farther west, and that they 

 had the general strike of the undoubted Pebidian rocks found along 

 the Caledonian Canal. That the}'' will, however, in time have to be 

 separated from the latter is certain, and that they moreover occupy 

 extensive areas in the Grampians, I have proved from careful 

 examination. At Tyndrum, and also in many areas to the north- 

 east and east, they are well exposed. Indeed, they may be said to 

 be the most important series in the Grampians ; hence I proposed to 

 Dr. Sterry Hunt that the}' should in future be separated from the 

 Pebidian under the distinctive name of " Grampian Series." 



Hendon, Dec. 1881. HknKY HiCKS. 



