124 



kind. Indeed, ranch that at first sight is suppo96<.l to be silicious sand, by apply- 

 ing the magnifyer, is found to be made up in a considerable degree of particles 

 of limestone ; and we cease to wonder at its productiveness. Instances are known 

 where banks of this kind of sand have produced better crops than the ordinary 

 soil adjacent. Much of this sandstone is so pure that it might be used in the 

 manufjicture of glass. It consists of particles of quartz, or pure silex, adhering 

 without any apparent cement. 



But there is another portion of the State where the sandstone, supposed to be 

 quite distinct from that above described, is red ; and, according to Dr. Norwood, 

 contains 3.9 per cent of alumnia and iron, and one per cent of carbonate of lime. 

 It eftervesces when acids are applied to it. This sandstone lies along the south 

 shore of Lake Superior, extending from the mouth of the Montreal river to be- 

 yond the western limits of the State. It has an average breadth of about twenty 

 or twenty five miles. 



The red marly clay found throughout the northern part of the State, and ex- 

 tending, in limited tracts, south of the N eenah, may be supposed to result from 

 the destruction of this red sandstone, and perhaps of other rocks of a similar 

 character. 



This marl every where furnishes a good soil as might be inferred from its 

 composition. Dr. jSTorwood"^' analyzed a sjDecimen from the Bois Brule river, 

 and found its constituent elements to be as follows : ^Yater, 8.0 — Silica, 41.1 — 

 Clay, 31.1 — Carbonate of lime, 4.1 — Carbonate of magnesia, 4.7 — Alumina 

 and oxide of iron, 9.0 — Loss, 2.0. 



The third division of the State, embracing all the southern and south-eastern 

 portions, and extending up the immediate valley of the Mississippi, is based upon 

 calcareous rocks. They consist of yellow, blue, and gi'ey varieties of limestone, 

 and are classed by o-eoloo-ists as " Silurian rocks," beina' of an affe lone: anterior 

 to the rocks of the coal formation. Although to the casual observer they appear 

 to lie in horizontal beds, it will be found upon closer examination that they have 

 a gentle dip or inclination. Those lying east of Rock river dip eastwardly to- 

 wards Lake Michigan, while those on the west dip towards the Mississippi. In 

 northern Illinois the same rocks dip towards the south and pass under the great 

 " coal basin"' of that State. 



The limestones in the western part of the State are composed of from forty- 

 seven to fifty-two per cent of carbonate of lime, combined with from thirty -eight 

 to forty-seven per cent of carbonate of magnesia. The other ingi-edients are, 

 principally, about six per cent of silex and two of oxide of iron. The limestones 

 of the eastern portion of the State have not been chemically examined, but they 



See Owen's Report, 1848, page .ST. 



