ELISHA MiTCHElvIv SCIENTIFIC SOCIETY. 31 



The manner in which these dikes cut the peridotites or 

 pass up throuofh the same opening- beside them, both 

 in this reg-ion and in a number of places in the adjoin- 

 ing- portions of Georg'ia, clearly indicates that the per- 

 idotites occupy areas of weakness in the g^neiss, through 

 which the dikes have found their easiest exit. It may 

 be stated here that no direct influence of the amphibo- 

 lite dikes upon the dunite was noted except an inter- 

 ming-ling- of the constituents of the two rocks along- 

 bands of three or four inches in thickness at the con- 

 tacts. 



Another character which is perhaps as important as 

 that of form, is the entire absence of lamination, or its 

 development to only a slig-ht extent, in the g-reat ma- 

 jority of peridotite outcrops. Dr. Julian, as noted 

 above, studied the outcrop at Webster, where the lam- 

 ination is so marked that the dunite bears a striking- 

 resemblance to a thin-bedded sandstone; and this is, in 

 fact, what Dr. Julian considered it to be. As pointed 

 out by Dr. Wadsworth, however, "the chief defect in 

 Dr. Julian's reasoning- is that all the evidence which he 

 g-ives in support of this view^ could exist equally well 

 if the rock had some entirely different orig'in. "^ If Dr. 

 Julian had only studied some of the typical massive du- 

 nite to be found within a day's journey of Webster, it is 

 safe to say that his conclusion on this point would have 

 been entireh^ different. 



Aside from the lamination in the body of the perido- 

 tite, there is often abundant evidence that it has been 

 subjected to considerable shearing in the schistose char- 

 acter of the talc along' the borders and in the frequent 

 slickensides encountered in the corundum-bearing- chlo- 



* Science. Ill, 1884, 486, 487. 



