26 The Ottawa Naturalist. 



once to identify the substance composing these porphyntic crystals with 

 the mineral described later by Dr. Thomson as " Huronite." The 

 source of these boulders was not known and the mineral never found 

 " in situ " until 1881 .when Dr. Robert Bell, (i)of Ottawa, in his examina- 

 tion of the country to the north-east of Lake Superior, noticed the 

 occurrence " of a dark grey crystalline diorite (in one place rendered por- 

 phyritic by spots of light-greenish yellow felspar) on the neck of land se- 

 parating Lake Mattawagaming from Lake Wabatongwashene.'' This rather 

 brief description was altogether inadequate to connect the mineral with the 

 Huronite which had previously been described by Thomson, and it was 

 not until Dr. Harrington, of Montreal, visited the spot on professional 

 business some year later, that the true identity of these " spots " was 

 clearly established. In 1891, Dr. Selwyn, of Ottawa, happened to be- 

 at the same locality which is situated between Missinaibi and Loch 

 Alch Stations on the main line of the Canadian Pacific Railway, and he 

 states that the dykes containing the Huronite cut both Huronian and 

 Laurentian strata. During the construction of the Canadian Pacific 

 Railway in 1884, Drs. Girdwood and Ruttan made a collection of the 

 principal rocks met with on the main line from Chalk River westward. 

 This collection, they subsequently presented to McGill University. 

 Among the specimens, was one of a dark green diabase with pheno- 

 crysts of a mineral resembling Huronite scattered through it. This 

 specimen had been obtained from a dyke cutting the granitoid gneisses 

 a few miles north-west of Pogamasing Station. The microscopical 

 examination, however, reveals the fact that the original DrutnmoiH 

 Island boulder was not derived from either of these localities. Mr. W. 

 G. Miller of the School of Mines, Kingston, who acted as Dr. Bell's 

 Assistant in 1893, mentions the occurrence of a dyke containing 

 Huronite near the contact between the granite and slates (Huronian) 

 at Depot Lake in the northern part of the Township of Proctor, about 

 fifteen miles north-east of Cook's Mills. From its geographical position 

 and the direction of the glacial striae this would seem to be the 

 most likely source of the Drummond Island boulder, although this 

 cannot be ascertained with certainty as the specimen from the locality 



(i) Report, Geological Survey, Canada, 1S80-2, part c, p. 4. 



