482 Wisconsin state agricultural society. 
the azoic formations. That is, the ore, especially the magnetic ore, rises 
above the surrounding country in elongated knobs, or mounds, sometimes 
assuming a conical form. Of this class of deposits, Pilot Knob, in Missouri, 
is a very good example. Two of these mounds or knobs are very near to 
Black River Falls. One on the west side of the river, along the foot of which 
the railroad track has been cut, where thus exposed, there is a mixture of 
magnetite and hermatite, and both considerably mixed with quartz. On each 
side of the ore, as thus exposed, there is a soft and somewhat irony slate 
rock, which appears to be thrown around the ore like a mantle, the slate be¬ 
coming softer as it passes away from the ore. Nothing has been done to 
determine the nature or extent of this deposit, save the excavations at its base 
for the railroad track. 
On the east of this mound, or a little to the south of east on the east bank 
of the river, is another of similar character and size, perhaps a little larger, 
where exposed along the river, it appears to be mantled around also with 
slate, mostly a micaceous slate, which in places is very much colored with 
the red oxide of iron. This mound remains in its natural state, no excava¬ 
tions made, covered mostly with small trees, brush and other vegetation, that 
forbid a close examination. Large and small pieces of the ore, however, lie 
scattered over the surface and in places protruding through the soil, from 
which we may infer that the mound is made up of similar material. A little 
further to the north, and perhaps an ofl-shoot from this mound, is a small 
knoll, or what looks like the upper part of a ledge of iron ore. This deposit 
was partially opened by a party who attempted to make iron here several 
years ago; several tons of the ore have been removed, leaving the ledge ex¬ 
posed for 100 feet wide and several feet high. The ore here is a fine grained, 
dark colored magnetite. A few rods still farther to the north is another ex¬ 
posure of ore, opened up also by the same party and exposed for several feet 
wide. The ore here is mostly the red hematite, but like the magnetite as ex¬ 
posed in the mounds, it is mixed more or less with silica in the shape of 
quartz. 
These are among the prominent deposits of iron ore in the immediate 
neighborhood of Black River Falls that I have examined. That there are 
others that I have not noticed in this one hasty visit to this place, or that may 
not yet be discovered by any one, I have no doubt. But these of themselves 
are sufficient, doubtless, to furnish ore for very extensive works for a period 
that will extend away into the future, to generations that are yet unborn. The 
question or questions, however, of their economic importance, and of the 
profitableness of making iron from these ores, must turn upon their purity 
and the cost of fuel, flux and building material for furnacesv 
These ores in their native state are not what we should call good merchant¬ 
able ores. The amount of silica mixed with the oxide of iron in the form of 
quartz, varying in different parts of the deposit from 15 to 35 per cent., must 
very materially injure their market value in this respect. It is true this ore 
can be “ dressed up ”— to use a mining phrase — to a 70 per cent. ore. That 
is, by separating the quartz from the oxide of iron, we can make it almost 
