1855.] 



FORBES — FOLIATION OF ROCKS. 



171 



Fig. 3. — Section of gneiss, limestone, and granite, at Stampekjtjern, 



on the Heights above Christiansand, Norway. 



W. E. 



a, a. Gneiss. c, c. Bands of augitic gneiss in the limestone. 



b, b. Foliated, crystalline, pink A, A. Granite (each band is about 10 ft. thick). 



limestone. 



30° to 45° East. The strike inclines in course of the foliation about 

 10° towards S. 



The section here represented is E. and W. nearly, or at right 

 angles to the strike ; and, coming from the east, we have first the 

 gneiss, which sometimes is slightly granitic, but always preserves its 

 regular foliated structure ; — next we find a bed, about 14 feet thick, 

 of coarsely crystalline pink limestone, in which a beautiful foliated 

 arrangement is visible (as shown in the specimens now exhibited), by 

 the presence of numerous small crystals of a green augitic mineral and 

 white scapolite. Sometimes these minerals are so abundant as to 

 present a very striking appearance, at other times we have only single 

 lines of these crystals, with the intermediate limestone free from 

 them ; in all cases, however, both in this bed and throughout, they 

 arrange themselves in distinct lines, which are invariably parallel to 

 the lines of foliation of the gneiss itself. No tendency to split along 

 these hues is present. Next we have some small beds (c c) of what 

 may be termed gneiss, but in which the same augitic mineral appears 

 to replace the mica, giving the mass a green appearance. The beds 

 between this and the granite are of limestone, similar to the above, 

 but of white colour and foliated in the same way. 



The granite (A), which now shows itself and is about 10 feet thick, 

 is composed of white felspar, quartz, and black mica, is coarse-grained, 

 and follows the general line of the beds. On its sides, where it 

 touches the limestone, it is in some places impregnated to a small 

 depth, but very strongly, with the same green augite ; and in cavities 

 at the junction we find aggregations of garnets, scapolite, and augite, 

 sometimes finely crystallized. 



Beyond the granite we have beds of white limestone like the 

 former and similarly interstratified, if we may use the term, with beds 

 of augitic gneiss, until we again come to another and larger vein or 

 bed of granite, of similar character to the former band, and under 

 which we again find the regular gneiss, still preserving the unaltered 



