November 19, 1908J 



NA TURE 



69 



IHE GEOLOGY OF THE CRAMPIASS.' 



'T'HERE are few parts of the British Isles which 

 •'■ can rival the southern Highlands ol Scotland 

 fur beauty and variety of scenery. Over much of 

 this district the genius of Scott has thrown the 

 glamour of romance, and year after year crowds 

 of tourists visit the scenes which he has rendered 

 famous. The flat vales which lie to the south of 

 the mountains (the plain of Strathmore) afford an excel- 

 lent contrast to the bolder hill country behind them. 

 Even the most stolid traveller who enters this region 

 may be expected to feel some curiosity regarding the 

 urigin of the scenery and the history of the rocks 

 which meet his eyes. Not a little has been written 

 on tlii-; subject, but much of it is contained in scientific 

 memoirs and periodicals which are beyond the grasp 

 of the untrai[ied g-eologist. The country, especially 

 the Highland portion of it, is of great complexity, 

 ,uid its structure has given rise to discussions, many 

 (if which are far from settled at the present time. 

 The task which the author of this work has essayed 

 is one of considerable ditTiculty. He 

 aims at giving' an account of the 

 geology and physiographical develop- 

 ment of this intricate region which 

 shall be intelligible to the unscientific 

 and at the same time thoroughly 

 abreast of the most recent researches. 

 He has achieved a large measure of 

 success even in the most difficult part, 

 while some of his chapters, such as 

 those on glaciation and scenery, are 

 excellent. The result is a book which 

 is at once interesting to the layman 

 and useful to the professed geologist. 

 The great boundary fault which 

 runs across -Scotland from Stonehaven 

 to the Firth of Clyde separates the 

 Highlands from the vallev of Strath- 

 more, two districts which are as dif- 

 ferent in their geology as in their 

 scenery and economic development. 

 To the north lie metamorphic schists 

 and gneisses of unknown age ; to the 

 south are fossiliferous Old Red Sand- 

 stone and Carboniferous rocks. One 

 volume is assigned to each of these 

 subdivisions. Much of the southern 

 Highlands has been mapped by the 

 Geological Survey, which has pub- 

 lished maps (and in some cases 

 memoirs also. Mr. Macnair. is well known for 

 his investigations on the metamorphic rocks of 

 Perthshire, and is familiar with a large part of the 

 area he undertakes to describe. His researches have 

 led him to conclusions not essentially different from 

 those of the Survey officers, 'whose opinions and ob- 

 servations he frequently quotes. He accepts the 

 current theories that as we proceed northwards from 

 the Highland border we pass over a succession of 

 slates, grits, gneisses, mica schists, and limestones, 

 which are not only apparently but actually in ascend- 

 ing order. They vary in lithological character and 

 in degree of metamorphism, but are essentially an 

 unbroken and continuous succession, the quartzite of 

 Schiehallion and Ben-y-gloe being the highest, while 

 the grits and slates of Leny and Aberfoyle are the 

 lowest rocks of the district. Two series of igneous 

 rocks are found among the sedimentary schists, one 



1 " The Geology and Sc nerj* of the Grampian'; 

 more." By P^ler Ma'iiair 2 V0I5. Vol. i., pi 

 xii+.99. (Glasgow: Jam-s MacLeho<c and So 

 ■21s. net. 



NO. 2038, VOL. 79] 



older and another later than the period of folding 

 and metamorphism. The former comprises the horn- 

 blendic schists, which are especially common around 

 Loch Tay, and the acid gneisses of Ben Vuroch ; 

 among the latter may be placed the granitic bosses 

 of Garabal Hill, Glen Lednock, &-c. Mr. Macnair 

 describes what, in his opinion, is the structure of 

 the country, and gives sections showing a series 

 of complex fans and synclinoria the axes of which 

 have a north-east trend. Although these hypotheses 

 are accepted by probably the majority of the geolo- 

 gists who are working in this district at the present 

 time, they cannot by any means be regarded as estab- 

 lished on any firm basis of proof. The apparent up- 

 ward succession is quite possibly misleading. Many 

 strong reasons may be advanced against it, and the 

 structure is not more clear than the sequence. Apart 

 from this, Mr. Macnair's account of the geology of 

 the Grampians is clear and judicious, and may be 

 recommended to those who wish to get a general 

 idea of the subject without too much detail. 



The second volume begins with a description of the 



nd the Valley of .Strath- 

 .tiv+ros ; vol. ii., pp. 

 J, 1908.) Price, 2 vols. , 



Old Red Sandstone (Upper and Lower) of Strath- 

 more. This vast sedimentary formation has always 

 had a strong attraction for Scottish geologists. The 

 author has given much time to its study ; he dis- 

 cusses it with enthusiasm, and attempts to prove that, 

 contrary to the usual opinion, the deposits are of 

 marine origin, and at one time completely buried the 

 Highland mountains. The arguments he brings for- 

 ward are not new to geologists, and, we must con- 

 fess, are, in our opinion, far from convincing; the 

 old theories of Godwin .Austen, I^amsay, and Sir A. 

 Geikie are not yet disposed of and out of date. These 

 chapters contain, however, many observations which 

 are little known and well worth placing on record. 

 The Carboniferous rocks occupy only a very small 

 area, and are not otherwise important. 



As might be expected in a region of such varied 

 topography, the glacial and alluvial deposits are of 

 considerable importance. The chapters devoted to 

 them and to their effect on the scenery of this part of 

 Scotland are the most readable in the book, and should 

 prove interesting to anyone who cares for geology 



