288 
CEMENT MATERIALS AND INDUSTRY. 
[BULL. 245 
The composition of the t}^pical shales and slates of the upper par 
of the Hudson formation is well shown by the following- analyses: 
Analyses of Hudson shales and slates in Pennsylvania and New Jersey. 
- 
Silica (SiO a ) 
Alumina (A1 2 3 ) 
Iron oxide (Fe 2 3 ) ... 
Lime (CaO) 
Magnesia (MgO) 
Alkalies 
Carbon dioxide (C0 2 ) 
Water (H a 0) 
68.62 
12. 68 
4.20 
1.31 
1.79 
3.73 
3. 00 
4.47 
2 
3 
68.00 
56. 60 
14.40 
21. 00 
5. 40 
5. 65 
2.68 
3.42 
1.51 
2. 30 
.11 
.50 
2.30 
2.20 
2.70 
3.00 
"76. 2! ' 
I 13.11 
2.6' 
a Insoluble. 
1. East Bangor, Pa. Twentieth Ann. Rept. U. S. Geol. Survey, pt. 6, p. 43f>. 
2. 1 mile northwest Colemanville, N. J. Geology New Jersey, 1868, p. 136. 
3. Delaware Water Gap, N. J. Geology New Jersey, 1868, p. 136. 
4. Lafayette, N. J. Rept. New Jersey State Geol. for 1900, p. 74. 
As above noted, the rocks of the Lehigh district have a general dip] 
to the northwest, though there are numerous local exceptions to this j 
rule. The lowest beds of the Hudson series, therefore, are thost 
which outcrop along the southern boundary of the formation, as abovti 
outlined. These lowest beds carry much more lime and less silicaa 
alumina, and iron than the higher beds whose analyses are given 
above. The lowest beds of the Hudson shales become more call 
careous and form a natural transition into the underlying cemeni 
rock or Trenton limestone. 
MANUFACTURING METHODS. 
COMBINATION OF MATERIALS USED. 
Throughout most of the Lehigh district the practice is to mix witl 
a relatively large amount of the ''cement rock 1 ' or argillaceous lime 
stone a small amount of pure limestone, in order to bring the Him 
carbonate content up to the percentage proper for a Portland-cemen 
mixture. As above noted, all of the u cement rock" is derived from 
the middle part of the Trenton formation, where the beds will rm 
from 60 to 70 per cent of lime carbonate. The pure limestone whicl 
is required to bring this material up to the necessary percentage o< 
lime carbonate (about 75 per cent) is obtained either from the lowe:< 
portion of the Trenton itself or from certain low-magnesian bed,; 
occurring in the Kittatinny formation. 
In the plants located near Bath and Nazareth, however, the practic< 
has been slightly different. In this particular area the cement-rocl 
