Q. W. Card — Flexibility of Rocks. 



123 



But if the fractured surface of the rock is examined, an abundance 

 of sheeny patches point to a crystallization of the cemeiiting matrix, 

 and these crystals offer a number of planes in various directions 

 along which solution proceeds with greater rapidity than elsewhere ; 

 and as a result the rock becomes divided into irregular interlocking 

 aggregates of sand and calcite." ^ The mode of interlocking in both 

 varieties is illustrated by drawings. 



Section of Flexible Limestone from the coast, a little south of Sunderland 

 [see ante, pp. 118-120). 



t *x " '' 



'i,: *. 



-.-'»--,*• > cr^'. * 







*-• 



1 



I* t 



y/ij' 



V 'nVif 



-r". -^ 



i)e?. ffflo. TT". Card. 

 EiG. A. — Flexible Limestone cut transverse to bedding, and showing 

 empty spaces, x 10. (p. 119.) 



Del. Ger. W. Card. 

 Fig. B.— Flexible Limestone highly magnified, x about 400. (p. 120.) 



An examination of a section of the North Carolina material in 

 the collection of this institution gives similar results : the quartzes 

 are very clear, have very irregular outlines, and are generally iu 

 direct contact ; thei-e are a number of cavities, and apparently an 

 articulation of the grains, while mica is present in very small 

 quantity only. 



3. It will now be useful to briefly compare these " sandstones " 

 with the Durham Limestones. In thin laminee the flexibility is very 

 similar in degree ; Leibner found that a strip of Carolina Sandstone, 

 very similar in dimensions to the strip of limestone used by myself, 



1 p. 54. 



