:l.J 
PENNSYLVANIA. 
287 
ha.se of the formation it is often a fairly massively bedded dark-gray 
limestone. Even so, it can usually be readily distinguished from the 
jnagnesian Kittatinny limestone, described below, for the cement rock 
s always darker than the magnesian limestone and contains none of 
he chert beds which are so common in the magnesian rock. 
The Lehigh cement rock is never nearly so high in magnesia as is 
he underlying Kittatinny limestone. It does, however, carry consid- 
rable magnesia (as compared with other Portland-cement materials) 
hroughout its entire thickness, and few analyses will show less than 
: to 6 per cent of magnesium carbonate. The following series of 
nalyses is fairly representative of the lower, middle, and upper beds 
»f the formation. The specimens from the upper beds, near the Hud- 
on shales, show considerably less lime and more clayey matter than 
hose from the lower parts of the formation. 
Analyses of Trenton limestone {Lehigh cement rock). a 
• 
2 
3 
4 
5 
fi 
7 
■ 
9 
10 
iilica (Si0 2 ) 
1.86 
5. 03 
8.38 
11. 90 
11.71 
11.11 
17.04 
22.71 
19. 53 
24. 45 
Llumina (A1 2 3 ) 
.60 
2.06 
4.03 
4.42 
4.36 
4.40 
6.90 
5.84 
6. 03 
5.68 
ron oxide (Fe 2 
3 ) 
.51 
1.23 
1.32 
1.70 
1.62 
1.91 
2. 13 
2.13 
1. 70 
1.57 
jime (CaO) 
53. 64 
49. 73 
45. 45 
44.18 
43.47 
42.51 
37. 53 
36. 50 
35. 71 
35. 00 
Magnesia (MgO) 
.81 
1.02 
1.34 
1.18 
1.82 
2.89 
2.17 
1.69 
3. 33 
2.21 
"arbon dioxide 
(C0 2 ) 
43. 03 
40.19 
37.18 
36. 01 
36. 15 
36. 57 
32. 88 
30. 52 
32. 73 ;29. 89 
a Ann. Rept. New Jersey State Geologist, 1900, p. 95. 
The specimens whose analyses are given above were mostly from 
■he vicinity of Belvidere, N. J., and, though representative in other 
espects, seem to have been rather lower in magnesia than the usual 
*un of the Trenton limestone in the Lehigh district. 
HUDSON SHALES. 
This series includes very thick beds of dark-gray to black shales, 
^ith occasional thin beds of sandstone. In certain localities, as near 
Slatington and Bangor, Pa., and Newton, N. J., these shales have 
been so altered by pressure as to become slates, the quarrying of 
which now supports a large roofing-slate industry. 
The geographic distribution of the Hudson shales and slates in the 
Lehigh district can be indicated only approximately without the pre- 
sentation of a geologic map of the area. It may be said that they 
cover practically all of Northampton, Lehigh, and Berks counties 
north of a line passing through Martins Creek, Nazareth, Bath, 
Whitehall, Ironton, Guthsville, Monterey, Kutztown, Molltown, and 
Leesport. 
