854 C. K. LEITH 
origin as dikes, which have been intruded along the planes of 
foliation. 
Smyth* describes pre-Cambrian diabase dikes cutting the granites 
and gneisses of the Admiralty Group of the Thousand Islands, St. 
Lawrence River. On Ge LASTEST, 
* A group of diabase dikes among the Thousand Islands, St. Lawrence River, by 
C.H.SmytH. Trans. N. Y. Acad. Sci., Vol. XXIII, 1893-4, pp. 209-214. 
