Hawortu. | Geology of Lead and Zine Ores. 67 
the conditions found in Missouri, in that the Upper Burling- 
ton, as spoken of by Shepard and Adams, consists in part of 
a shaly limestone. This limestone from 1090 feet to 1358 
feet is remarkable for the large amount of flint it carries, and 
without doubt is exeedingly hard to drill. It corresponds to 
the Upper and Lower Burlington. The 6 feet of shale be- 
low this heavy bed of limestone may or may not correspond 
to the Hannibal shales of Shepard. The 96 feet of sand- 
stone lying between 1364 and 1460 feet is an iron-stained 
rock, which certainly was formed near the surface where 
weathering action could exert an influence upon it. It is 
a hard rock with numerous large fragments of chert. The 
4 feet of limestone, and again the 8 feet of limestone closing 
at 1490 feet, are both quite arenaceous, carrying roundec 
grains of sand in fairly great abundance for a limestone. 
Also, they are somewhat dolomitic, but not nearly so much 
so as the limestone further down. The 99 feet from 1490 to 
1589 feet is much more dolomitic than the sandstone above. 
For this reason it was thought best to include the upper sand- | 
stone in the Mississippian and the lower in the Devono-Car- 
boniferous, although it should be stated that the line of 
demarkation is somewhat arbitrarily drawn, as the evidence 
from a six-inch hole in the ground by no means is conclusive. 
The large mass of dolomitic limestone beneath 1589 feet is 
remarkably arenaceous throughout, which fact is implied in 
the drawing by the whole limestone mass being stippled. In 
some instances it was difficult to draw an exact division line 
between the limestone and the sandstone. Here we have a 
great mass of interbedded dolomitic limestone and sandstone 
corresponding fairly well with the Silurian limestone and sand- 
stone of southern Missouri and northern Arkansas. Whether 
or not any of it is Devonian cannot be told, and, therefore, 
the name Devono-Silurian is used in the drawing to avoid 
arguments. 
One interesting and important fact should be noted, namely, 
the total absence of shale below the 1364 feet level. The 
Devonian shales which Professor Van Hise” has emphasized 
so strongly are entirely absent, unless the 6 foot body of 
29. Van Hise, Prof. C. R.: U.S. Geol. Surv., 22d Ann. Rep., part 2, p. 49. Washington, 1901. 
