206 CEMENT MATERIALS AND INDUSTRY. [bull. 243. 
Lewis, F. H. The plant of the Bronson Portland Cement Company, Bronson, Mich. 
Engineering Record, Apr. 30, 1898. 
Ries, H. Clays and shales of Michigan. Mich. Geol. Survey, vol. 8, pt. 1, pp. 1-67. 
1900. 
Russell, I. C. The Portland-cement industry in Michigan. Twenty-second Ann. | 
Rept. U. S. Geol. Survey, pt. 3, 1902, pp. 629-685. 
PORTLAND CEMENT RESOURCES OF MINNESOTA. 
Of the limestones occurring in Minnesota, only one is usually suf- 
ficiently low in magnesium carbonate to be worth considering as a 
Portland cement material. This is the limestone described as " Tren- 
ton" in the section on Iowa, pages 147-165 of this bulletin. Mr. Ulrich 
states that this nonmagnesian formation is well developed in southern 
Minnesota, particularly in the vicinity of Wyckoff and Spring Valley. 
The pure limestone beds in these localities are both underlain and over- 
lain by shale, which might prove available for use in the mixture. 
PORTLAND-CEMENT RESOURCES OF MISSISSIPPI. 
No cement of any type has ever been manufactured in Mississippi, 
but several large limestone areas occur in the State, and at least one o§\ 
these is so well located with respect to fuel supplies and transporta- 
tion routes as to give promise of being of future importance as a; 
source of Portland-cement material. 
The available limestones of the State may be grouped and described 
under three heads, the third being the most promising as the possiblee 
basis of a cement industry. 
The three groups noted are: 
(1) Mississippian (Lower Carboniferous) limestones. 
(2) Cretaceous limestones (Selma chalk or " Rotten limestone"). 
(3) Tertiary limestones (Vicksburg limestone). 
The distribution of these formations is shown on the geologic map 
(PI. II), which is based on recent work by the United States Geological 
Survey in Mississippi. 
MISSISSIPPIAN ("LOWER CARBONIFEROUS") LIMESTONES. 
In the extreme northeastern corner of Mississippi, in the counties 
of Itawamba and Tishomingo, there is a small area of Devonian andi 
Carboniferous rocks. These include shales, thin sandstones, and 
limestones. The limestones, which are mainly of Mississippian (Lowen 
Carboniferous) age, are frequently low in magnesia, and are otherwise ] 
suitable for use as Portland cement materials. At present, however, 
the most promising localities of these limestones have no adequate 
transportation facilities. This fact, together with the nearness of the ] 
soft and easily crushed Selma chalk, will probably serve to prevent 
the utilization of the Carboniferous limestones in the near future. 
