122 CARBONIFEROUS LIMESTONES 
’ white and rather gelatinous precipitate, having a slight tinge of green; with caustic 
potash, a copious white, gelatinous precipitate, partly soluble in excess; the alkaline 
solution, after filtration and saturation with hydrochloric acid, gives a precipitate 
by supersaturation with ammonia. Hy drosulphuret of ammonia produces a copious 
black and white precipitate, each remaining distinct if the liquid be not shaken. 
With carbonate of ammonia, a copious white precipitate; with ferrocyanide of 
potassium, a light blue precipitate; with oxalate of ammonia, little or no precipi- 
tate; with chloride of barium, a copious white precipitate, insoluble in nitric acid ; 
with nitrate of silver, a slight white precipitate, increasing by standing, and darken- 
ing in the rays of the sun; with chloride of platinum, a slight yellow precipitate. 
These reactions with chemical reagents show that it is an acid solution of sulphate 
of alumina, sulphate of potash, sulphate of protoxide of iron, and a little chloride 
of potassium and sodium. It is, in fact, a double alum of potash and protoxide of 
iron. The same kind of water was observed at several other localities on the 
Upper Des Moines. 
About two miles above the Forks, on the left bank, two beds of coal are seen ; 
the main one lies about twenty feet above the water-level; the other bed, which is 
only four to six inches thick, lies above, and is separated from the former by about 
one foot of shale. Seams of a grayish clay run vertically and diagonally through 
the principal coal-bed. 
About one mile higher, on the same side, a thin bed of coal is exposed, near the 
water-level, associated with argillaceous and ferruginous shale, depositing in their 
course a gelatinous, hydrated oxide of iron. 
At several points between the last-mentioned localities and Hunt’s Bend, desig- 
nated on the chart of the river, a gray limestone occurs, a few feet above the 
water-level. By exposure, this caleareous rock turns brown, no doubt from the 
peroxidation of the iron. It is charged with Productus Flemingu ; Cardina nana 
also occurs in it. Both above and below it are argillaceous shales, as seen on 
Section No. 42, D. The upper shale includes nodules of ironstone, and septaria, 
veined with red calcareous spar. Towards the summits of the ridges near by, under 
the drift, there is a white limestone; at a lower level, soft sandstone, like that at 
the Forks, and still lower, a bed of coal. The relative thickness of this bed, and 
the exact order of superposition, cannot be satisfactorily seen. Some of the darker 
limestone will probably answer for making an hydraulic limestone. 
On Section 10, Township 80 north, Range 25 west, are alternations of red, 
purple, and gray shales, as shown on Section No. 48, D. The red and purple shales 
have somewhat the appearance of red pipe-stone, but are much softer, and subject 
to disintegration; they leave a pale red streak, approaching in character to the 
soft red, argillaceous ochres, known to carpenters under the name of “keel.” Three 
to four miles higher up, is another bank of the same character. (See Section 49, D.) 
On Section 14, Township 81 north, Range 25 west, a gray productal limestone is 
elevated thirty-five feet above the water-level, with a bed of shale and coal beneath 
it, as seen on Section 44, D. In the shale, some crystallizations of selenite were 
collected. The shale between that and the productal limestone includes septaria 
and calcareous blocks that may afford hydraulic cement. 
