282 DR. C. A. MATLEY ON THE [May I906, 



sea-erosion has channelled out the softer and more argillaceous beds 

 (see fig. 3, below). It should be noticed that the erosive action of 

 the sea here follows the bedding-, not the cleavage-planes, this being 

 due to the fact that while the soft argillaceous beds are still well- 

 cleaved, the harder calcareous bands are only imperfectly fissile in 

 the cleavage-direction. 



Fig. 3. — Upper Rush Slates, on the shore south of Rush Harbour, 

 looking eastward. 



[The beds dip steeply northward, while the cleavage dips steeply in the 

 opposite direction. The strike is east and west. The softer argillaceous 

 beds are eroded, leaving the calcareous beds standing out as ridges.] 



The upper slates above the third limestone-band [R 6 />] are more 

 calcareous than those below. Nodules and lenticles of impure lime- 

 stone are found in them at many horizons ; while seams and beds of 

 purer limestone which have resisted cleavage are occasionally inter- 

 calated. About 480 feet above R6 b is a prominent bed [118 a], 

 some 6 feet thick, composed of lenticles of limestone (one of them 

 5 feet thick) embedded in a black slaty matrix. The slates con- 

 tinue for about 300 feet above this zone, and then pass, after about 

 40 feet of Passage-Beds, into the Rush Conglomerates. Pebbles in 

 the upper portion of the Rush Slates, although decidedly rare, are 

 occasionally to be found, and there is a 1-inch seam [R 9 a] of 

 fossiliferous limestone containing numerous tiny quartz-pebbles as 

 low down as 120 feet below the Passage-Beds. 



The Pas sage -Beds, about 40 feet thick, are intermediate in 

 character between the Rush Slates and the Rush Conglomerates. 



