346 Methods of Stratigraphy. — Winchell. 
is seen in the early Esquisse geologique du Canada and in 
the geological map accompanying the Geology of Canada of 
1863. Those maps do, in a general way, include strata not 
described in the text, nor embraced in the sections, even 
ignoring some Laurentian areas. The original Taconic was 
roughly laid off in the maps of Emmons, in the same way. 
The descriptive text, however, and the main idea which the 
author intended to express, should be the guide in determin- 
ing how to interpret him, instead of the map, for the map is 
designed only to illustrate the idea— not the idea the map. 
If the/ author's idea be found at variance with his map, by 
later research, every fair geologist will correct the map instead 
of the idea. This should be done for the correct Huronian, 
no less than for the correct Taconic. 
We have, then, three conceptions of the Huronian which at 
different times have been dominant with the Canadian geolo- 
gists. 
1. The original Huronian of Logan and Murray, consisting 
of fragmental strata, and including the Keweenawan, 1855-63. 
2. The "greenstone" Huronian of Bigsby and Hunt, 1863. 
3. The expanded Huronian of the present officers of the 
Canadian survey, embracing some of the primordial quartzytes'" 
and extending downward to the "Laurentian." 
Principles of Stratigraphy employed. It will be an inter- 
esting inquiry to seek for the principles that were relied on by 
the various geologists in arriving at the foregoing results. Sir 
"William Logan, beginning the Canadian survey in 1842, with 
Alexander Murray as assistant geologist, was a pioneer not 
only in the geology of Canada, but of the world. Much of the 
nomenclature of the science now in vogue has been based on 
work done either in Canada or elsewhere since that date. Very 
little positive knowledge of the composition of the earth's 
crust, or of the alternation and succession of its various parts, 
then existed. Every rock-terrane below the Potsdam sand- 
stone was at first regarded as "primitive." Subsequently the 
"metamorphic" strata were recognized existing below the Pots- 
dam sandstone and above the gneiss, though these also were 
generally regarded as "primitive," a word to which some 
'"The Huronian quarrzytes of the Thessalon valley are fostiiliferons 
in IMinnesota with Parados ides and Lingula. Thirteenth report of the 
Minnesota survey, p. G5 ; Amekic.\n Geologist, March, 1888. p. 177. 
