OF DYNAMICAL GEOLOGY BAILEY. 189 



V. JOINTS, CLEAVAGE, ETC. 



The divisional planes referred to above are of such common 

 occurrence in regions of metamorphic or partly metarnorphic 

 rocks, such as form so large a part of Nova Scotia, as hardly to 

 deserve notice here. And yet their recognition and distinction 

 from each other and from planes of bedding is one of the most 

 serious practical difficulties to be encountered by the field 

 geologist, especially in the study of the Cambrian rocks of the 

 southern coast. The quartzites of this system abound in joint 

 planes, often causing them to divide into prismatic blocks, while 

 the slates of the same system have in general a strongly pro- 

 nounced cleavage structure. Both may be, and often are, much 

 more pronounced than the bedding planes, so that strata which 

 are really level-lying, or in low undulations, may present the 

 appearance of being highly inclined. Such a condition of things 

 is especially prominent over much of the country north of 

 Caledonia in Queen's County, where, were it not for the fact that 

 the rocks are strongly banded or ribbanded with somewhat 

 strongly contrasted colors, indicating the true planes of deposi- 

 tion, mistakes might very readily be made as to their true posi- 

 tion. Portions of the coast south-east of Lunenburg, where 

 similar strongly ribbanded beds occur, afford other illustrations 

 of the same fact. 



Besides the joints which characterize the massive quartzites 

 of the Cambrian, or the granite by which the latter is invaded* 

 it is proper to notice here the similar divisional planes found in 

 the traps of Digby Neck, Briar Island, &c. Some of the columns 

 thereby determined are illustrated in Plate v. (Part 1 of the 

 present volume of the Transactions,) as seen at Israel Cove on 

 the Petite Passage, and others much more remarkable occur 

 along the south side of Briar Island. 



VI. METAMORPHISM. 



Almost every stage of the metamorphic process may be well 

 studied along the coasts of the south-western counties. The 

 uuartzites, as might be expected, show the least evidence of 



