100 



FOLIATION, 



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TJPPEB 



Gallery. 



absence of relation is more than doubtful if universally ap. 

 .* plied ' Professor Henslow observed, in 1821, that the folf 



Wall-case 45. x * «j? A t. i/»at * lun- 



ation ot the rocks of Anglesea bears a general relation to 



the planes of bedding. This I can verify from personal 



The same is the case in the Island of Arr 



an. 



knowledge. 



(Case 46,) but it has been shown that the metamorplrism 

 of the Anglesea rocks preceded the disturbances that pro- 

 duced cleavage. There is, therefore, no necessary con- 

 nection between cleavage and foliation, and it may now 

 perhaps be considered at all events as a near approach to 

 the truth, "that if rocks be uncleaved when metamor- 

 phism occurs, the foliation planes will be apt to coincide 

 with those of bedding ; but, if intense cleavage has preceded 

 then we may expect that the planes of foliation will lie in 

 the planes of cleavage." (Ramsay, " Geological Quarterly 

 Journal," 1853, vol. ix, p. 172.) 



The relation of proximity of granite and gneissic rocks 

 is obvious, and, from their constant occurrence together, it 

 may be considered that they are intimately related, the 

 gneissic structure being in some manner connected with 

 the fusion of associated granite. All geological evidence 

 tends to prove that, as a rule, large masses of granite 

 rocks cooled and consolidated slowly and deep beneath 

 the surface. One result of this would be that, the 

 rocks in contact with granite would also for a long time 

 remain in a heated condition, and if a partial softening 

 took place, or by any process the rock got into such a con- 

 dition that internal movements of its particles occurred, 

 then, these might probably congregate according to their 

 affinities, in layers, wherever circumstances would allow, 

 and most likely showing a tendency to form in the direc- 

 tion of pre-existing lines of stratification when these formed 

 the principal planes, or of cleavage when it had been so 

 strongly superinduced that the rock would split in the 

 cleavage planes in preference to those of stratification. 





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