240 Miller on the Taconic. 
thick called catlinite, largely used for the manufacture of pipes. 
The quarry is thirty miles north of the southwest corner of the 
state and four miles east of the west line. The Sioux quartz- 
yte occurs in the north-west corner of Iowa. 
The geological extent of these rocks in Canada is very great. 
They may be traced from near lake Tematscaming, 80 miles 
north-west of lake Nipissing, southwestward to lake Huron, 
and from thence westward, on the north shore of the lake and 
the north shore of lake Superior, and on beyond lake of the 
Woods, a distance in all of about 800 miles. They pass beneath 
the lakes and expose a large area in the upper peninsula of 
Michigan, at Marquette and Menominee, and a great thickness, 
extending from the lowest to the highest Taconic, as first ascer- 
tained by Houghton; thence they pass into Wisconsin, exposing 
a large area and quite as complete a representation of the series, 
while another arm extends from Duluth into Minnesota. The 
thickness in Michigan is about four miles, but in Wisconsin, in- 
cluding the Copper-bearing series which is three-fourths of ig- 
neous material, the thickness is much greater, and even exclud- 
ing the igneous material the thickness exceeds four miles. The 
upper part of the Taconic system in Wisconsin, formerly called 
" The Copper-bearing series," has received the unattractive 
name of the Keweenawan formation, from Keweenaw point, 
but as it is part of the Taconic system, the preferable name is 
the older one of the "Copper-bearing series." The rocks ap- 
pear between Scoresby bay and cape Cresswell, in latitude 
82° 40' N., where Nares and Feilden called them Cape Rawson 
beds. In 1856 Emmons divided the system into Upper and 
Lower Taconic. The Canadian geologists, in 1S63, placed the 
Upper Taconic in the Silurian system, and called it "Lower" 
Potsdam, which name therefore became a synonym. The only 
geographical names which have been used to subdivide the 
Upper Taconic into groups, which seem, in the present 
state of learning, to be worthy of retention, are in descending 
order, the Swanton group, the Georgia group and the St. 
John's group — if in fact the last is below the Georgia and there- 
foi'e not a synonym. Emmons placed the Stockbridge lime- 
stone in the Lower Taconic, but it would seem from the exami- 
nations made by others that his division would have been more 
