254 
THE TERTIARY VOLCANOES 
BOOK VIII 
component lavas is shown in Fig. 286. As a further detailed illustration 
of the general succession of the basalts in the Skye plateau, I give a dia- 
grammatic view of the largest of Macleod’s Maidens — the three weird sea- 
stalks that rise so grandly in front of the storm -swept precipice at the 
mouth of Loch Bracadale. The height of the stack must be at least 150 
feet (Figs. 284 and 287). About ten distinct sheets of igneous rock can be 
counted in it, which gives an average thickness of 1 5 feet for the individual 
beds, ft will be observed that there is a kind of alternation between the 
Fig. 287. — Section of the largest of Macleocl’s Maidens. 
compact, prismatic basalts and the more earthy amygdaloids, but that the 
former are generally thickest. 1 
These features, which are repeated on cliff after cliff, may be con- 
sidered typical for all the plateaux. Another characteristic point, well 
displayed here, is the intervening red parting between the successive 
beds. If the occurrence and thickness of this layer could be assumed 
1 A striking and illustrative contrast between the relative thickness of the beds of the two kinds 
of rook is supplied by the line sections of this district. The amygdaloids range from perhaps 6 
or 8 to 25 or 30 feet ; but the prismatic basalts, while never so thin as the others, sometimes 
enormously exceed them in bulk. In the island of Wiay, for example, a bed of compact black 
basalt, with the confused starch-like grouping of columns, reaches a thickness of no less than 170 
feet. Its bottom rests upon a red parting on the top of a dull greenish earthy amygdaloid. It is 
possible, however, that some of these columnar sheets of basalt are really sills. 
