182 
CEMENT MATERIALS AND INDUSTRY. 
[BULL. 
for example, is highly magnesian, while the stone from Texas and! 
other localities is just as low in magnesia as the best of the Trenton! 
limestones. 
Analyses of metamorphic '.( Trenton ?) limestones from Maryland. 
Silica (Si0 2 ) 
Alumina (A1 2 3 ) 
Iron oxide (Fe 2 3 ) 
Lime carbonate (CaC0 3 ) 
Magnesium carbonate (Mg0O 3 ) 
0.60 
Trace. 
Trace. 
98.53 
.87 
13. 6 
5.1 
77.8 
3.1 
1. Texas, Baltimore County. J. Higgins, analyst. Third Rept. Maryland Agric. Chemist, p. 77. 
2. Highlands, Howard County. H. J. Patterson, analyst. Eighteenth Ann. Rept. U. S. Geo 
Survey, pt. 5, p. 1059. 
ADJACENT CLAYS AND SHALES. 
In case a Portland-cement plant is projected to utilize the mor 
clayey t}^pes of the Trenton limestone — material like the Lehigl 
cement rock, for example — a small amount of pure limestone will b 
needed for mixture with this clayey limestone in order to bring it u 
to the proper composition for a Portland-cement mixture. In th 
case the requisite pure limestone can readity be secured from the lowe 
portion of the Trenton limestone itself, this lower portion being usuall 
a rock carrying from 93 to 98 per cent of lime carbonate. 
The following analyses are of surface clays from near Williamspor 
Washington County, used by the Conocheague Brick Company. 
Analysts of surface days from Maryland. 
[H. Ries, analyst.] 
Silica (Si0 2 ) 
Alumina ( A1 2 3 ) 
Iron oxide (Fe 2 3 ) . . . 
Lime (CaO) 
Magnesia (MgO) 
Alkalies (K 2 0,Na 2 0). 
Combined water 
Moisture 
67.50 
17. 20 
6. 70 
.45 
.33 
1.76 
5.90 
.20 
2 
3 
n. d. 
61. 
n. (1. 
22. 
n. d. 
3. 
0.22 
n. (1. 
n. d. 
2. 
n. d. 
8. 
n. d. 
1. Dark-red clay. 
2. Light-red clay. 
3. Light-gray clay. 
H. Ries, analyst: Md. Geol. Survey, vol. 4, p. 473. 
