366 The American Geolor/isf. December, 1894 
ent beds of sandstone, limestone, shale and chert, a general 
section of which is given in the following table : 
General section of the Paleozoic strain in nortliern Arkansas, 
Feet . 
1. Millstone grit, coarse sandstone 400 
2. Black shah- and shelly limestone 50 lo 250 
3. Archimedes limestone, partly crystalline 50 to 80 
4. Shaly sandstone 20 to 200 
5. Black argillaceous shale 100 to 250 
(i. Yellow ferruginous sandstone 50 to 170 
7. Black argillo-calcareous shale 30 to 300 
8. Chert and limestone 370 
9. Sandstone, coarse, rounded grains • 40 
10. Black argillaceous shale 2 to 50 
11. Crystalline limestone 100 to 155 
12. Compact blue limestone 280 
13. Saccharoidal, white triable sandstone 5 to 150 
14. Magnesian limestones, chert, and sandstone ... . 1,600 
Not all of the above are exposed on any one slope. Proba- 
bly in no case is the immediate slope more than 2,000 feet 
above the stream, the average hillsides being 500 to 1,000 feet. 
Yet over the entire area each formation is exposed in many 
places, generally four or five or more on each slope. 
Not all of the above beds extend over the whole area. 
Numbers 1, 6, 8, 13 and 14 are persistent, occurring at all 
points in the area where the proper horizon is exposed. Num- 
bers 9 and 10 are very irregular, rarely both being present at 
the same time, and frequently both being absent, or if present 
only an inch or two in thickness. Numbers 11 and 12 are 
persistent beds over the eastern half of the area, but are 
wholly absent from the western half, so that at many places in 
the western part of the area No. 8 rests directly on No. 10, 
where it is present, and on No. 13 in the absence of No. 10. 
The significance of this will appear in what follows. 
Springs are abundant all over the area, some noted for me- 
dicinal properties and all remarkable for the clearness, purity 
and volume of the water. One, the Mammoth spring, forms a 
river in itself; and from many others now large-sized creeks. 
While springs occur in almost all of the above formations, 
by far the greater number, possibly more than half, the 
springs of the whole area emerge on No. 10 or No. 13 of the 
acconipaivving section. The cause for the emergence on No. 
10 is ver} T plain, as it is a compact argillaceous shale; but it 
