88 



SCIENCE 



[Vol. V., No. 104. 



groups of crystalline schists of the Atlantic 

 belt in North America, I declared, in an ad- 

 dress before the American association for the 

 advancement of science, in 1871, my convic- 

 tion that the crystalline schists of the Scottish 

 Highlands " will be found ... to belong to a 

 period anterior to the deposition of the Cam- 

 brian sediments, and will correspond to the 

 newer gneissic series of our Appalachian re- 

 gion." My studies of these, and of similar 

 crystalline rocks in North America, in the 

 British Islands, and in continental Europe, 

 served in succeeding 3'ears to confirm this 

 conclusion as to the gneiss of the Highlands, 

 which was again asserted before the geological 

 society of London in 1881. 



Meanwhile the attention of able workers in 

 Great Britain had been turned to this great 

 problem in Scottish geology, beginning with 

 Jlicks in 1878, and followed by Callaway and 

 Lapworth, all of whom labored independently 

 of each other, but with concordant results. 

 Their separate conclusions, as announced from 

 time to time, but more fully in 1883, agreed in 

 showing that the views of Murchison and his 

 followers were altogether untenable, and in 

 disaccord with the facts of stratigraphy. Ac- 

 cording to the results of these observers, pub- 

 lished early in 1883, there are seen in the 

 Highland region an older granitoid or Lauren- 

 tian gneiss, and a } T ounger series, consisting in 

 large part of tender gra}' gneisses and granu- 

 lites, with mica schists, which are the charac- 

 teristic rocks of the Highlands, and have been 

 variously named Upper Pebidian. Grampian, 

 and Caledonian. They are indistinguishable 

 from the younger gneisses of the Alps, and 

 from the Montalban of North America, to 

 which they were already referred in 1871. The 

 unconformable superposition of the younger 

 upon the older gneissic series, and the fact that 

 the Cambrian strata rest unconformably upon 

 both, and are younger than either, are also 

 shown. The existence of great parallel north 

 and south faults, with upthrows on their east 

 sides, bringing up successively higher rocks ; 

 the fact that these faults pass into sigmoid 

 liexures, in which both the younger gneiss and 

 the Cambrian rocks were involved ; and also 

 that the 3'ounger gneiss is made to overlie the 

 latter 03- dislocations, which were accompanied 

 by a great thrust from the east, throwing both 

 series into a succession of folds overturned to 

 the west, giving the whole region a general 

 eastern dip, — were made apparent, as may be 

 seen in the various papers of Hicks, particu- 

 larly that in the Quarterly geological journal 

 for Ma}', 1883, with appended notes by Bon- 



ney, and in the papers in the Geological maga- 

 zine for the same year, b} T Callawa3' and by 

 Lapworth, the latter entitled ' The secret of 

 the Highlands,' besides a later one by Calla- 

 wa3^ in the same magazine for May, 1884, on 

 Progressive metamorphism. An abstract of 

 these results will be found in a chapter on the 

 progress of geology, in the Smithsonian report 

 for 1883. 



The publication of these conclusions im- 

 pelled the geological surve3 T of Great Britain 

 to direct its attention to the region for the pur- 

 pose of defending, if possible, the previously 

 expressed opinions of the official geologists ; 

 and, after investigations carried on in 1883 

 and 1884, the conclusions of the director, A. 

 Geikie, and of his assistants, Messrs. Peach 

 and Home, are given in Nature for Nov. 13, 

 1884, and reprinted in the American journal 

 of science for Januaiy, 1885. Therein, while 

 making no special reference to the results 

 obtained b3 T his immediate predecessors, Geikie 

 abandons entirely the views hitherto held by 

 him in common with Murchison and Ramsay, 

 and confirms those of Hicks, Callawa3 r , and 

 Lapworth. He writes that he has " found the 

 evidence altogether overwhelming against the 

 upward succession which Murchison believed 

 to exist in Eriboll from the base of the Silurian 

 [Cambrian] strata into an upper conform- 

 able series of schists and gneisses," and adds, 

 " that there is no longer any evidence of a 

 regular conformable passage from fossiliferous 

 Silurian [Cambrian] quartzites, shales, and 

 limestones, upwards into crystalline schists, 

 which were supposed to be metamorphic Silu- 

 rian sediments, must be frankly admitted." 

 The same conclusions are also reached by Geikie 

 from the re-examinations of similar sections in 

 Rossshire, previous^ described by himself in 

 accordance with the views of Murchison. The 

 preliminary report of Messrs. Peach and Home, 

 with a general section, explains the structure 

 in complete accordance with the statements 

 alreacty made b} 7 late observers, as explained 

 above. 



Geikie, in the paper just cited, calls attention 

 to the laminated and schistose structure devel- 

 oped by the great pressure and friction along 

 the lines of movement in the displaced gneis- 

 sic and hornblendic rocks, and also to similar 

 changes produced b3 T the same agency in de- 

 trital rocks, such as arkose in this region. Both 

 of these structural alterations au nparently 

 included by Geikie under the head of what he 

 calls a ' regional metamorphism.' This, how- 

 ever, is a misapplication of the term, likely to 

 confuse and mislead the reader, since local 



