146 
ROYAL SOCIETY OF CANADA 
being the Eparchæan Interval, and the one beneath the lower Huron- 
ian (—Upper Huronian) being the next in importance. 
The gneisses, 
etc., of the Laurentian are not given a separate formational name, 
probably because as eruptives they were not considered entitled to 
one. 
If we fill out the Bureau of Mines classification to the form of 
the other two and omit the Cambrian in which all are alike, the three 
compare as follows: 




BUREAU OF MINES LAWSON VAN HISE 
Keweenawan Keweenawan Keweenawan 
(Unconformity) (Unconformity) (Unconformity) 
Animikie Animikie Upper Huronian 
(Unconformity) (Unconformity) (Unconformity) 
pate 0 | 
(Eruptive unconformity) 
Upper Huronian Huronian 
: Lower Huronian 
(Unconformity) = Upper Keewatin ; 
(Unconformity) (Unconformity) 
{ Laurentian, so-called \ 
Lower Huronian Ontarian Archean 
(including Vermilion 
series, schists and 
gneisses) 
(including Keewatin 
(Unconformity) and 
Coutchiching) 
(including Iron Range, 
pyroclastic schists and 
eruptives) 


It is apparent that if the Laurentian gneisses be left out as 
eruptives the three classifications correspond very closely both as to 
formations and as to unconformities, though, after the Keweenawan, 
the nomenclature of the third column has each name shifted one 
place upward as compared with the other two, the Archean taking 
the place of the lower Huronian or Ontarian. It is understood, of 
course, that the whole series is included in the Archean in the first 
two columns, and all but the last is included in the Algonkian in 
the third. 
The differences between the first and second columns are chiefly 
in regard to the place of the Laurentian and the occurrence of an 
unconformity between the Keewatin and the Coutchiching. At Michi- 
picoton and in many other Huronian localities there is no doubt that 
the Laurentian is later than the upper Huronian, as shown in former 
