Geology of St. Helens Island. 53 



to them it may be given to elicit from nature hitherto 

 hidden secrets and add something to the domain of useful 

 knowledge. The twentieth century sets out on its career 

 in the investigation of the vegetable kingdom in circum- 

 stances far more favorable than those in which the 

 botanists of a hundred years ago were situated ; and one 

 has only to cast his eye over the array of the prominent 

 workers in this field as set forth in the recently formed 

 International Association of Botanists, to feel assured that 

 a still more rapid advance may be counted on in the years 

 that lie before us. 



Geology of St. Helen's Island. 1 



By A. W. Nolan and J. D. Dixon. 



Introduction. One of the most interesting formations 

 in the vicinity of Mount Eoyal is a breccia, which occurs 

 in isolated patches at several points in the district. The 

 best known exposure is found on St. Helen's Island, 

 situated in the St. Lawrence Eiver, opposite the City of 

 Montreal. The breccia also occurs on He Sonde, north 

 of St. Helen's, on He Bizard, at White Horse Eapids, 

 Eiviere des Prairies ; and in small fissures in the Trenton 

 limestone near Pointe Claire, and at McGill University. 



1. A detailed geological survey of St. Helen's Island formed part of the Honour 

 Course in Geology and Mineralogy in the Faculty of Arts of McGill Universty for the 

 session of 1901-100?. The present paper embodies certain results of the examination of 

 the Island, which seem especially worthy of record. 



