82 Reviews — Macnair's Geolorjij of the Granqiians. 



ranges form respectively the northern and southern limbs of a faulted 

 and denuded anticline. The lavas are also associated with the Lower 

 Old Red conglomerates, whicli rest on the Highland schists. 



Chapter xii, on the dolerite dykes, which traverse the rocks of 

 Highlands and Lowlands alike, is illustrated by a number of good 

 photographs of these intrusions. The author is inclined to think that 

 the large dolerite dykes of Perthshire, trending nearly east and west, 

 are of late Carboniferous age, whilst those with a north-westerly trend, 

 occurring mainly in the western districts, are undoubtedly a con- 

 tinuation of the Tertiary dykes of the Western Isles. 



The succeeding chapter is devoted to a sketch of the glaciation of the 

 whole region. The ordinary phenomena — rock striations, boulder- 

 clay, erratic blocks, moraines, rock-basins, raised beaches, and forest beds 

 — are taken up seriatim and local examples cited. On the question of 

 interglacial periods we find the indefiniteness, coupled with more or less 

 contradictory statements, which we have had to remark on previously. 

 jFirst, we read that there are at least two great phases, an older period 

 of general glaciation and a later period of valley glaciers. Further on 

 (p. Ill) beds of sand, gravel, fine clay, and layers of peat intercalated 

 in the boulder- clay, are quoted as evidence of the great changes of 

 climate, and proof that the boulder-clay is not one continuous deposit. 

 " In the one case we have a state of matters where no life is possible, 

 away down in the depths of the ice, where there is no sound but the 

 sound of the river of ice and rock, an incessant, hollow, monotonous 

 grind ; in the other we have light and heat, the brightness of sun- 

 shine with all the cheerfulness and beauty which it brings, the fl.utter 

 of forest leaves, the song of birds, the hum of the busy insect's wing, 

 and even, perchance, in the later of these periods, suggestions of the 

 presence of man." How many interglacial periods are represented 

 between the bottom and top of the boulder-clay ? The localities 

 where the layers of peat in the boulder-clay are found are not 

 mentioned. We could understand the author arguing for the 

 existence of an interglacial period between the deposition of the 

 boulder-clay and the accumulation of the moraines at the mouths of 

 the Highland glens, yet he states (p. 117) that "after the great 

 ice-sheet passed away, local glaciers still continued to occupy the 

 valleys", indicating therefore a continuity of glacial conditions. 

 A remarkable confusion of personalities is caused by a large perched 

 block near Callendar being called " Samson's putting stone " in the 

 text and "The Deil's Puttin' Stane " in the photograph. The 

 chapter finishes with some notes on the distribution of the so-called 

 Alpine flora of the hill-tops. The author concludes that the strain- 

 slip-cleavage of the Een Lawers schist "has been a most important 

 factor in determining the present existence of Alpine plants on these 

 mountains ". 



A long description of the river-terraces of the Tay and Tummel, and 

 a discussion of their origin, occupies the greater pai't of chapter xiv. 

 It concludes with some notes on the silting up of lochs, on soils, and 

 on peat. 



In the final chapter, on the relation of the scenery to the geological 

 structure, a summary of the geological history of the region is given 



