380 



SIR A. GE1KIE ON THE TERTIARY 



[May 1896,- 



exhibits long parallel lines, probably marking flow-structure, which, 

 are made conspicuous by a pale yellow, ferruginous, weathered crust. 

 Portions of the larger intrusive sheet have been broken off and 

 involved in the later rock. The observer cannot fail to be impressed 

 by the prodigious force with which the sills were injected, when 

 he sees here that a thick sheet of solid dolerite has been actually 



Pig. 23. — Section of dolerite-sill cut by another sill, both being 

 traversed by dykes, Rudh' an Tasgaich, western side of Sleat, Shye. 



d a- 



split open along the middle. The younger sill disappears to the 

 north, and is not found in the cliff of Rudha Charn nan Cearc, 

 where the thick sill, lying once more on the band of conglomerate, 

 forms a fine escarpment above the shore. Dykes of fine-grained 

 basalt with compact chilled margins rise through both sills, together 

 with veins which pursue a wavy upward path like strips of black 

 ribbon. 



Pig. 24. — Sill traversing bedded basalts, cliffs of Strom'o, at 

 the entrance of the Vaagbfjord. 



[The caves and notches shown at the bottom of the precipice mark the position 

 of the vents represented in PI. XV. and figs. 8, 9, & 10.] 



In the Paroe Islands the actual base of the volcanic series* is 

 nowhere visible. Hence, the great lower platform of intrusive 

 sheets being there concealed, this feature of the basalt-plateaux is 

 less conspicuous than it is in the Inner Hebrides. A number of 



