Geolofiy of the Lake Superior JReyion. — Winchell. 15 
Dans la formation corrospondante de la rive septentrionale du lac 
Huron, on rencontre dt-s gres ayant un aspect plus vitreux et des con- 
jiiomerals plus abondants que sur lo lac Superieur, associes pourtant 
avec des schistes et, des conglomerats schisteux semblables a ceux que 
nous venous de decrire. le tout ott'rant de grandes masses intercalees de 
diorite. Une couche de calcaire ayant une epaisseur de seize metres 
forme une partie de cette serie, a laquelle M. Logan donne une puis- 
sance de plus de trois mille metres. M. Logan a constate, ai>res I'ir- 
ruption des diorites interstratifiees, celle de deux systemes de dykes de 
diorite, et une troisieme de granite d'une epoque intermedi;iire entre 
ces deux derniers. La formation des veines metalliferes appartient a 
une epoque plus recente encore. Les especes principales de ces veines 
sonl le cuivre natif, le quartz, le spath calcaire, la dolomie, la fluorine 
et la barytine avec plusieurs zeolithes, dont la plus abondante est la lau- 
montite: on y rencontre en outre la heulandite, la stilbite, la thomson- 
ite, rapoi)]iyllite et Tanalcime, ainsi que la prehnite et le datholite. 
Ces veines ne sont metalliferes que lorsqu'eiles traversent lescouchesde 
trapp. 
This statement, which doubtless was designed to embody 
the results of the Canadian survey to that date, covering the 
researches of Logan and Murray, on the Huronian of the 
region, is remarkable for three things: 
1. The Huronian is made the equivalent of the Lower Cam- 
brian of Sedgwick. 
2. The Huronian includes the whole copper-bearing series 
of the region, including what is now styled Keweenawan. The 
little colored map which accompanies the work also demon- 
strates that. 
3. The Huronian is said to be nonconformable on the Lau- 
rentian. It is probable that the locality about five miles east 
of the mouth of the Thessalon river, in the original Huronian 
region, was depended on for authority for this statement. 
In 1863 Logan issued his great summary of Canadian ge- 
ology,* in which he varies somewhat from the Esquisse of 1855. 
The assumed parallelism of the Huronian with the Lower 
Cambrian is not mentioned, and the copper-bearing rocks are 
divided into two series — the upper and the lower volcanic 
groups. These are said to lie non-conformably upon the Hu- 
ronian, the upper group in the original Huronian region and 
the lower group in the Thunder Bay region. The two togeth- 
*Geology of Canada: Rei)orf of progress from the commencement of 
the siu'vey to ISO.']. Montreal, 180:], with an atlas. 
