80 Reviews — Macnair's Geology of the Oramjnans. 



IV. — The Geology and Scenery of the Grampians and the 

 Valley of Strathmore. By Peter Macnair, F.li.S.E., F.G.S., 

 Curator of the Natural History Collections in the Glasgow 

 Museums, etc. 2 vols. pp. xiv + 195 and xii + 199, with 

 163 plates and 10 folded and coloured maps and diagrams. 8vo. 

 James MacLehose & Sons, Glasgow. 



{Concluded from January Number, p.\i5.) 



IN the fifth chapter, on the schistose igneous rocks, the sill-like 

 forms of basic rock, which occur amongst the schists of sedimentary 

 origin, are dealt with first. There is much reference to ancient views 

 on the origin of these rocks, but the author fails to give a satisfactory 

 account of their present structure, of the changes that they are 

 thought to have gone through, or of their original constitution. The 

 account of the general distribution of the sills is apparently taken 

 from the publications of the Geological Survey, and Cunningham- 

 Craig's description of the sill on Ben Vrackie is wrongly ascribed to 

 Barrow. The description of the so-called 'older' granite of Ben 

 Vuroch and of neighbouring masses is apparently drawn from the 

 same source. 



Chapter vi is devoted to a discussion of the structure of the southern 

 Grampians. The author adopts the well-known theory of mountain 

 building, which assumes a sinking geosynclinal area in which a thick 

 mass of sediments is deposited. Through tangential earth-pressure 

 the sediments are converted into a geanticlinal, compressed further 

 and ultimately rucked up into a series of isoclinal folds, arranged in 

 anticlinoria and synclinoria. 



- Applying this theory to the Highlands, the author finds that the 

 main axis of upheaval of the range passes through the Ben Lawers 

 ridge, and can be traced in a south-westerly direction into the district 

 of Loch Awe. Along this line the axial planes of the folds are 

 vertical, and on each side of it they dip in towards it. The dip of 

 the limbs of the folds decreases as one recedes from the central line. 

 It is noticeable that in this ' fan ' the youngest beds lie in the central 

 line, where, according to the theoretical 'fan,' the oldest beds should 

 crop out. 



The author describes in some detail numerous sections taken from 

 the central ' fan ' right across country to the southern border of the 

 Highlands. These are thought to prove the existence of another great 

 'fan' named the " marginal /acA^-r." A part only of this fan is 

 preserved to us along the Firth of Clyde, since the Highland boundary 

 fault runs obliquely across its northern limb and cuts it out 

 completely in Perthshire. The axis of the intervening synclinorium 

 is described as running up through Cowal, and after bending sharply 

 eastward is thought to enter the boundary fault near Ben Venue. 

 Along this axis the author believes that the beds are arranged in 

 a synclinal double fold, and considers the anticline of bedding of the 

 older geologists and the anticline of foliation described by Clough in 

 the memoir on the Geology of Cowal to be entirely deceptive. We 

 have failed, however, to find the double synclinal fold in the sections 



