73 



Dr. M*'Culloch's Additional R€7}iarks on Glen Tilt. 



Perfectly formed crystals of calcareous spar are rare in this place ; but I 

 have recently observed the two varieties known by the name of the dog-tooth 

 and the nail-head, together with the primitive rhomb. 



DisTHENE. — This is the last of the substances which I have discovered in 

 Glen Tilt since my original paper was drawn up, and with it I shall close 

 these miscellaneous remarks. It occurs in a vein of quartz traversing mica- 

 ceous schist, in two different places. In one, it is of its most ordinary blue 

 colour; in the other, of a pearl gray. It is imbedded in the quartz ; but one 

 end of the prism is invariably fixed in the schist in which the vein is contained. 

 Otherwise, it presents no peculiarity requiring a detailed notice. 



