kt:l.] ILLINOIS. 135 
In the cut on the Illinois Central Railroad north of the zinc-smelting 
orks at Lasalle the following section is shown: 
Section near Lasalli , ///." 
Feet. 
( 1 ) Green and ash-gray shales 4 
( 2 ) Nodular calcareous shale : ; 
( 3) Greenish shale 12 
(4) Impure chocolate-colored limestone 2 
(5) Red and green shales LO 
(6) Green shaly clay 8 
(7 ) Shaly limestone 6 
(8) Upper main limestone 12 
(9) Green shale 2 
(10) Lower limestone 12 
Beds 8, 9, and 10 of this section, taken together, represent bed No. 
of the preceding section. The shale parting which here separates 
e two limestone beds increases in thickness farther south, until at 
iru 6 or 8 feet of shale intervene between the two beds of limestone, 
lis limestone series occurs at about the horizon of coal bed No. 9 
the Illinois reports, and is probably the same as the limestones 
posed near Carlinville. 
COMPOSITION. 
The Coal Measures limestones, though usually high in clayey impnri- 
is, are commonly low in magnesium carbonate. The analyses given 
the following table are of the more argillaceous limestones. Anal- 
es of purer rocks, used at three Portland-cement plants in the State, 
11 be found on pages 136 and 137. 
Analyses of Coal Measure limestones from Illinois. 
ica(Si0 2 ) 
umina (A1 2 3 ). 
)n oxide (Fe 2 3 ' 
me (CaO) 
7.54 
3.43 
45. 57 
ignesia (MgO) . . . : I 4. 36 
2 
3 
4 
5 
17.11 
18.54 
13. 89 
19.49 
1.97 
3. 91 
2.61 
3.71 
44.44 
42. 03 
45.91 
41.75 
1.12 
1.54 
1.00 
1.21 
10. 27 
15. 32 
38. 49 
2.41 
-5. Lasalle County. 
Sugar Creek, Sangamon County, H. Pratten, analyst. Geology of Illinois, vol. 1, p. 60. 
PORTLAND-CEMENT INDUSTRY IN ILLINOIS. 
Four Portland-cement plants are at present in operation in Illinois. 
iree of these plants use limestones and shales from the Coal Mens 
es; the fourth utilizes a mixture of blast-furnace slag and limestone. 
a Kept. Geol. Survey Illinois, vol. 7, p. 46-47. 
