IMPORTANCE OF FORMATION 4 OF THE NEBRASKA SECTION. 325 



Near First Cedar Island, a very singular bed makes its 

 appearance, superimposed on No. 3, which we shall con- 

 sider as probably forming a local upper member of that 

 formation. It extends up the Missouri Eiver to a point 

 near the Great Bend, a distance of about eighty miles. 

 Lithologically it is a dull black, unctuous clay, destitute 

 of any grit, and does not effervesce with an acid. It 

 contains some carbonaceous matter and great quantities 

 of selenite in crystals.] 



This formation, as stated above, probably occurs on the 

 North Branch of the Saskatchewan, at the Coal Falls. 



FORMATION NO. 4 OF VERTICAL SECTION. 



[This formation is the most important one in the Cre- 

 taceous system of the north-west, not only in regard to 

 its thickness and its geographical distribution, but also in 

 its influence on the agricultural capabilities of the country. 

 It is only second in interest to the succeeding bed in 

 the number, beauty, and variety of its organic remains. 

 Commencing about ten miles above the mouth of James 

 Eiver, where it is seen only in thin outliers capping the 

 distant hills or bluffs, it continues gradually assuming a 

 greater thickness as we ascend the Missouri until reaching 

 the Great Bend, where it monopolizes the whole region, 

 giving to the country underlaid by it a most gloomy and 

 sterile aspect. At the Great Bend it attains a thickness 

 of 200 feet, and continues to occupy the country border- 

 ing on the Missouri to the mouth of Grand Eiver, where, 

 in consequence of the dip of the strata, it passes gradually 

 beneath the level of the river. 



After dipping beneath the water level between Grand 

 and Cannon Ball Eivers, this formation again rises to the 

 surface about thirty miles below the mouth of Milk Eiver 

 (far up towards the sources of the Missouri), by a reversed 



Y 3 



