^^^ The American Geologist. November, i.h93- 
from tlie upper strata. A few miles south oi' Dubuque crevi- 
ces are met with identical in every respect with the ore-bear- 
ing fissures farther north, but instead of carrying lead and 
zinc, except in small amounts, they are decorated with great 
numbers of stalactites and stalagmites. The ore deposits of 
this region have evidently had the same origin as these lime 
formations, and no one questions the fact that the latter are 
due to moisture trickling down from above. 
In order that the theory of lateral secretion may be well es- 
tablished it must be shown that the metals are diffused 
through the country rock. The necessary analyses have not 
been made for the Iowa region, but Winslow in his Lead and 
Zinc Report* shows that the limestones and cr^^stalline rocks 
of Missouri do contain small quantities of these minerals. 
"The amounts of metallic lead vary from about 0.0004 to 
0.007 per cent., of metallic zinc from about 0.0002 to 0.018 per 
cent., and of copper, manganese and barite there are corres- 
pondingly small amounts. It thus appears, on this hypothe- 
sis, which does not require that the ores should come from the 
immediately adjacent rocks, that the metalliferous contents of 
the countr}^ rocks are ample to supply the ore deposits." 
There is every reason to believe that the Galena limestone 
of Iowa also contains small quantities of lead and zinc and 
that these have been leached out by percolating waters and 
deposited in the crevices. It is not uncommon to find small 
particles of galena antl sphalerite in the different dolomitic 
formations of the state. In the Oneota small pockets of lead 
are very common and denote the presence of this mineral in 
considerable abuntlance. 
THE DEVONIAN SERIES IN SOUTHWESTERN 
MISSOURI. 
By OscAE H. Hershev, Freeport, 111. 
Ill publications of the Missouri Geological Survey, and in 
.)ther writings bearing on the stratigraphy of southern Mis- 
souri, we find occasional mention of a black shale occurring 
between the limestones and sandstones of the Ozark series and 
the Kinderhook group in Stone, Barry, and McDonald coun- 
ties, Mo., and extending into Arkansas, which has been re- 
ferred to the Devonian system. This bed of shale is well de- 
*Missouri Geol. Surv., vol. vii, p. 478, 1894. 
