1855.] 



FORBES FOLIATION OF ROCKS. 



173 



case, in which the Unes of fohation are carried out quite independently 

 of the nature of the minerals hy which they are formed. 



It will be understood by referring to fig. 1, p. 167, where we have 

 an overlying granite (A), below this a bed of ordinary black micaceous 

 gneiss (a a), sending forth a small arm (6), very quartzy and losing 

 itself in the surrounding white, coarse-grained, crystalline limestone 

 {d), of which a thickness of about 8 feet is uncovered and is here 

 represented ; in this we find several blackish detached patches of 

 gneiss (c). 



The line (//) crossing the lower part of the section represents 

 an apparent line of bedding, very regular, and showing itself the more 

 strongly, from the foliation of a few inches on the upper side princi- 

 pally being much closer than throughout the rest of the mass. This 

 line, as shown in the section, runs nearly E. and W., or at right 

 angles to the strike, and inclines 20° from N. to S. The strike itself 

 is within a few degrees of N. and S., and inclines 15° to E. 



The portions of the limestone marked e in the section, fig. 1, are 

 foliated by crystals of blackish-green to light-green augite and white 

 scapolite ; in the part marked ff the foliation is produced by the 

 presence of laminae of mica. Now when the lines of foliation are 

 examined, which are well developed and distinct, it will be seen that 

 these invariably run in one direction throughout the mass, no matter 

 what minerals produce the foliation itself; also that this direction 

 coincides with the line of apparent bedding. 



Not many yards above, and at right angles to this, the section 

 represented in fig. 5 was made, showing as much as was uncovered 



Fig. 5. — Section of granite, gneiss, and limestone at Jcegersborg, 

 near Christiansand, Norway. 



A. Granite. 



a. Granitic gneiss. 



b. Ordinary gneiss. 



Foliated crystalline limestone. 



c. 



by soil or debris. This presents a much-disturbed appearance ; the 

 central part appears to have been broken through by a fault, and we 

 have on the east side, on the surface, granite (A) ; below this, gneiss 

 («), without grain, passing into regular gneiss (6), and then the 

 limestone (c c) cut up by granite. On the other side, the granite is 

 absent ; and we have gneiss, similar to the former and without grain, 

 at top, and then the limestone, in which rounded masses of granite 



