CONDITION OP THE SEDIMENTS. 



Similarity In Cape Breton the Cambrian rocks have much the same litho- 



sediments in logical appearance as they have in southern New Brunswick, and they 

 andother* " are ^ ar ^ened to about the same degree ; and do not, any more than 



parts of Nova the latter, exhibit areas of metamorphic rocks, except the included 

 ocotia 



islands and ridges of pre-Cambrian age. There are no intrusions of 



granite or other hypogene rocks, nor are there crystalline schists such 

 as are met with in the areas referred to the Cambrian system in the 

 mainland of Nova Scotia. 



The process of hardening is most marked in the sandstones, which, 



when in heavy bed*, are converted into pseudo-quartzites ; yet we 



never meet with a true quartzite in which the grains or particles of 



sand are invisible from the filling of the interstices between the 



Lime and iron grains with silica. While the cement is to a great extent silicious, 



silica common showing that the sandstones have been steeped in heated waters, yet 



cements of the fc ne strata often respond to the test for calcium-carbonate, an evidence 



Cambrian l 



rocks in Cape that the cement is in part calcareous. 



Breton. 



In the flags of the Johannian division of the St. John terrane, which 



split readily along mud-seams, or mica-besprinkled layers, there are 

 often numerous cross-joints filled with calcium -carbonate. When 

 weathered, these flags fall to pieces at the joints, and the surface of 

 the soil where they prevail, abound with angular sandstone fragments. 

 The corresponding middle portion of the Etcherninian terrane, which 

 is also quite arenaceous, carries a cement largely composed of car- 

 bonate or peroxide of iron ; the latter is often sufficiently abundant ta 

 give a strong colour to these sandstones, or even at times to concen- 

 trate to irregular thin beds of red hematite. The strength of the 

 cement which holds together the particles of the rocks of the middle 

 members of the Etcheminian and St. John terranes respectively cause 

 these members to stand out prominently; and they are consequently 

 visible in raised ridges when other parts of their respective terranes 

 are concealed from view by deposits of drift. They are therefore 

 useful in revealing the structure of the Cambrian terranes, which 

 otherwise would be difficult to unravel. 



Causes of The prominence of the middle member (Johannian) of the St. John 



lce * group, is the more marked because it is bordered both above and 



below by soft rocks. These softer members, originally mud-beds, are 



usually in the condition of slates ; often they are so cleft as to have 



no visible bedding planes. In all this region the cleavage planes have 



