2S0 
CEMENT MATERIALS AND INDUSTRY. 
[BULL. 243. 
by the presence of a high percentage of clayey matter, as is well 
shown in the " cement rock" of the Lehigh district. 
The following table of analyses shows the composition of samples 
of Trenton limestone from various localities in Pennsylvania. No 
analyses from localities in the Lehigh district are given in this table, 
as this district is discussed in considerable detail below (p. 284). 
Analyses of Trenton limestones, Pennsylvania.® 
1 
2 
3 
4 
5 
6 
7 
8 
9 
in 
11 
L2 
13 
II 
L5 
Silica (Si0 2 ). 
0.91 
4.38 
5. 88 
3.62 
.54 
.39 
.82 
.76 
4.30 
2. 51 
2.55 
8.41 
8.84 
.98 
2.66 
Alumina 
(A1 2 3 ), 
iron oxide 
(Fe,,0,). 
0.26 
.64 
1.68 
.19 
.20 
.32 
.38 
.43 
.36 
.60 
n. d. 
.57 
.81 
.26 
.26 
Lime car- 
bonate 
(CaC0 3 ). 
94.98 
91. 89 
90.39 
92.12 
97.89 
98.32 
97. 53 
97. 65 
86. 13 
90.63 
92.00 
86.36 
89. 18 
97. 32 
95. 07 
Magnesium 
carbonatej 
(MgC0 8 ). j 
3.87 
2. 88 
2. 
4.21 
1.2* 
1.1 
1.2 
l.i: 
8.8 
6.1 
\ . 54 
5. 24 
.96'li 
1 . 29 
1.04 
«From Reports Ml, M2, M3, Second Geol. Survey Pennsylvania A. S. MeCreath, analyst. 
1. Mount Etna Furnace, Blair County. 
2. Rodman Furnace, Blair County. 
3. 4. Tyrone, Blair County. 
5, 6, 7.*Shortlidge quarry, Belief on te, Center County. 
8. Campbell quarry, near Bellefonte, Center County. 
9, 10. Rutherford quarry, near Harrisburg, Dauphin County. 
11. Cumbler quarry, near Harrisburg. Dauphin County. 
12. Craighead quarry, Mount Holly, Cumberland County. 
13. Mont Alto. Franklin County. 
14. Williamson, Franklin County. 
15. Rauchs Gap, Clinton County. 
HELDERBERG OR LEWISTOWN LIMESTONE. 
DISTRIBUTION. 
The Helderberg limestone outcrops in central and eastern Pennsyl-1 
vaniain a series of narrow bands whose distribution is too complicated 
to be readil}^ described, but is shown on PL XIII. 
