ber. 
Place. 
Specimen num- 
1516J.| Bed of Montreal 
River, Ashland 
County, Wisconsin. 
1709..; Silver Islet Landing, 
north shore of Lake 
Superior, Ontario, 
Canada. 
1709A!| Same place as 1709. 
DETRITAL ROCKS. 
§ 
g 
Oo 
a 
2 ; 
3 5g 
|] Be} 
5 3 
i<g n 
NW. | 20 
iy 
a\¢ 
a 
é| 3 
47|1E. 
Dark-red; 
Macroscopic descrip- 
tions. 
Fine-grained; dark- 
gray; very hard and 
firm; effervesces 
with hydrochloric 
acid. SiOz, 55.91 
per cent. 
Very fine-grained; 
light yellowish- 
gray; hard and firm; 
has a semi-crystal- 
line aspect. A simi- 
lar sandstone from 
the same bed yielded 
Macfarlane: silica, 
72.89; iron oxide, 
0.91; carbonate of 
lime, 13.04; carbon- 
ate of magnesia, 
11.94. (Canadian 
Naturalist, new 
series, Vol. IV, p. 
39.) 
fine- 
grained; effervesces 
with hydrochloric 
acid. Macfarlane’s 
analysis of a similar 
rock from this vicin- 
ity (loc. cit.) gives: 
silica, 73.45; ferrous 
oxide, 2.41; carbon- 
ate of lime, 12.54; 
carbonate of mag- 
nesia, 10.94, 
133 
Tabulation of microscopic observations upon sandstones, &e.—Continued. 
Microscopic descriptions. 
The predominating fragments are from 
basic rocks. With these are rarer 
ones of a felsitic porphyry. Quartz 
particles are very rare. A cement of 
coarsely crystalline calcite pervades 
the whole rock, and makes up prob- 
ably as much as one-fourth of its 
mass. See Plate XVI, Fig. 2; also 
Vol. III, Geology of Wisconsin, p- 
200, and Plate XTX A. 
Small angular quartz particles make up 
the larger part of the rock. There 
are a few fragments of porphyry 
matrix. Infiltrated calcite and do- 
lomite, along with some infiltrated 
quartz, occupy the interstices of the 
fragments. The cleavage lines of the 
two former are only very rarely to be 
observed. 
Predominating angular quartz frag- 
ments are imbedded in an abundant 
red-stained earthy-looking matrix, in 
which must lie the calcium and mag- 
nesium carbonates indicated by the 
analysis, 
i rr ee eee eee ee 
