264 DESCRIPTIVE CATALOGUE 
shaly. Prevailing colour, gray; some beds, light gray. Composed of grains, both 
rounded and angular; very firmly united by an argillaceous cement. Some of the 
beds rather more compact than others. Some of the finer-grained, greenish-gray 
beds contain large rounded pebbles of argillaceous shale, embedded. May be com- 
pared with No. 418, though it contains less hornblende and felspar, and more quartz, 
than the Fond du Lac rock. It may also be compared with No. 451, St. Louis 
River, and No. 110. Not magnetic. Fracture, even and granular. Weathered 
surfaces somewhat uneven, and darker than the body of the rock. Joints of the 
dark-coloured and finer-grained varieties incrusted with a flesh-coloured mineral, 
probably felspar. 
649. Bears N.10° EK. Very fine-grained sandstone—like that brought from Gers- 
dorf, in Saxony. Colour, gray; minutely crystalline. Fracture, smooth; conchoidal. 
Jointed. Weathered surface black; scales off in thin crusts. Not magnetic. Very 
compact. 
650. Bears E. and W. Basaltic (?). Resembles No. 644. Very compact; fine- 
grained ; homogeneous. Lasily marked with the knife. Much like some of the 
metamorphosed fine-grained argillaceous slates. Numerous joints; difficult to get a 
fresh fracture. It may be compared with No. 588. Colour, gray, with a light 
bluish or purplish tint. Fracture, smooth and conchoidal. Joints, somewhat rusty. 
Weathers with a black surface; discoloured for the depth of one or two lines, the 
discoloration being of a yellowish-gray colour. Not magnetic. 
651. Bears E. and W. (nearly). Basaltic. Colour, very dark greenish gray, 
with a faint purplish tint. Very irregular, nodular fracture, in which it resembles 
Nos. 630 and 632. Amygdaloidal—the cells being filled, principally, with thalite, 
the dark olive-green magnesian mineral, which is also distributed liberally, in grains, 
through the body of the rock. Weathers with a dirty yellowish and greenish-gray 
surface ; iron-shot, but which does not fall off in scales. No. 115 is from the 
same locality. The body of the rock is nearly homogeneous, and shows no appear- 
ance of crystallization. It resembles most nearly the basaltite of Gottesberg, in 
Schlesien; and bears a great analogy to the dolerite of Steinheim. This dike, if 
continued westward, would strike Two Island River, about fifteen miles above its 
mouth. On that river, and south of the point where it would intersect the dike, is 
the great development of No. 188, which rock, together with the succeeding rocks, 
up to No. 193, inclusive, were probably derived from this or a similar dike. If the 
Two Island dike begins nearer the Lake, as it probably does, then the dike, if the 
same, bends to the N. and E., forming a southeasterly curve. The specimens 
brought from Two Island River, and which have been set down as volcanic grits, 
contain the same mineral (thalite) found in such abundance in the rock under con- 
sideration. They are, however, more granular and coarse in their structure, and 
contain a very large percentage of iron, giving them a deep red colour, but have the 
same nodular fracture. 
652. Volcanic grit, at the mouth of Two Island River. (See No. 190.) This 
rock was probably derived from No. 651. Contains the same mineral developed in 
No. 651, and also in No. 190, of Two Island River. 
653. Greenstone. Bears N. and 8. Runs under the Great Palisade. This is a 
