34 Een'eics — 3Iacnairs Geology of the Grampians. 



zone ; (2) the Lower Arenaceous zone, with the ' green beds ' at 

 the top ; (3) the Loch Tay Limestone ; (4) the Garnetiferous Schist 

 zone ; (5) the Upper Argillaceous zone ; and (6) the Upper Arenaceous 

 zone. This terminology is somewhat cumbrous, and the use of ' Upper' 

 and 'Lower' will appear premature to most geologists in view of the 

 difficulties of reading the Highland sequence. The author -writes 

 with remarkable assurance on this point. His main argument appears 

 to be that of Sir Archibald Geikie and the Geological Survey, viz. 

 that the simplest interpretation of the structure places each inner belt 

 above the succeeding outer one. This order is taken to be the order 

 of original deposition, but it is quite possibly illusory. In fact, if the 

 structural theory adojjted in a later chapter were applicable to the 

 Highlands as rigorously as the author would have us believe, we 

 should expect the oldest beds just where he puts some of his 

 youngest, i.e. along the axis of the denuded anticlinorium. 



The author then proceeds to a more detailed description of the 

 'zones', which would have been much easier to follow had the 

 names of the localities mentioned in the text been inserted in the 

 large geological map (on a scale of 6i inches to 1 mile) provided 

 at the end of the volume. Many more place-names could have been 

 inserted without obscm-ing the map. Commencing on the Highland 

 border, we meet first the Lower Argillaceous zone, comprising the 

 clay-slates of Aberfoyle, -which on the Clyde pass into the condition 

 of phyllites. Immediately to the north-west comes the Lower 

 Arenaceous zone, containing the massive grits of Ben Ledi and other 

 grits, greywackes, and more argillaceous schists, up to and including 

 the 'green beds'. The intense metamorphism shown by these rocks 

 around the head of Loch Lomond as compared with their development 

 elsewhere does not receive adequate treatment, Cunningham-Craig's 

 paper on the subject not being referred to. The peculiar 'green 

 beds ' receive a short description. Evidence proving their clastic 

 origin is brought forward, but their distinction from the intrusive sills 

 of epidiorite with which they have been confounded is left to be 

 inferred. In the Loch Tay Limestone zone schists on both sides of 

 the limestone are sometimes included. The course of the limestone 

 outcrops in the neighbourhood of Loch Tay is traced in unnecessury 

 detail, and the evidence afforded by the limestone of intense buckling 

 and compression is pointed out. 



To the north-west of the Loch Tay Limestone zone lies the 

 Garnetiferous Schist zone. This comprises a belt of mica-schists, 

 usually of considerable breadth, and traceable like the other zones 

 from sea to sea. Garnets occur throughout this horizon, not only in 

 the mica-schists, but also in the epidiorites and hornblende-schists. 

 The author considers that the garnets are a product of dynamic 

 metamorphism, apparently in the sense that they represent a phase 

 of the regional metamorphism, which increases in a general way 

 from the frontier towards the Central Highlands. Beyond the 

 Garnetiferous Schist zone lies the Upper Argillaceous zone, comprising 

 the belt of rocks known as Ardrishaig phyllites, calc-sericite schist, 

 or Ben Lawers schist, in the different districts which it traverses. 

 A band of black graphitic schist, cropping out along the north-west 



