and its associates on Lake Superior. 197 
The normal form of cement is a fine grained sandstone, com- 
posed apparently of the same material as the pebbles. Often 
the cement is very subordinate in volume, the pebbles touching 
each other. Frequently, however, the reverse is the case, and 
often the sandstone forms layers from less than an inch to many 
feet in thickness. 
_ The original character of the cement is often entirely lost; the 
interstices between the pebbles are sometimes, thoug rarely, 
empty ; in places the sand is associated with oxide of iron, chlo- 
rite, a white talc-like mineral, carbonate of lime, or it is entirely 
replaced by calcite, chlorite, epidote or even native copper. 
t is a remarkable fact that while all the conglomerate beds 
near Portage Lake are free from pebbles of quartz-porphyry, 
those in the neighborhood of Calumet are characterized by 
pebbles rich in grains of quartz. This abrupt change takes 
place about six miles N.E. from the lake. 
Different horizons of the Portage Lake series of rocks are 
Royale co rtion of very many of 
per-bearing bed, the upper portion of ve 
ape beds tate the many rdaliidal cavities filled with a light- 
gree : 
Width of 2 to 6 feet, form from 10 to 40 per cent of the rock, 
ized triclinic feldspar, delessite, prehnite and specular iro 
traps through a portion of this distance are frequently impreg- 
nated with e bgt, as is also the cement of the conglomerate beds. 
Stet ae ” property we come to a belt of the forma- 
ton in which many beds have a tendency to a eee cae 
stalline texture, and in some the character is highly se 
veloped, giving the rock, at a distance, almost the oe side : 
: ofa chloritic granite. Still farther west, on the ‘‘ Souths! eH 
a berty, the brown amygdaloids often present a scorlaceo 
-“Ppearance which is quite characteristic. 
