118 The American Geohxjlst. AuRust, isj)r). 
on account of the great hydrostatic pressure. As the waters rise 
through the irregular channels enlarged from cracks and seams, the 
pressure decreases and more and more of the dissolved gas escapes from 
the water until at last, when the surfac3 is reached at the various 
spi-ings, the gas emerges with the rythmic flow due to the irregularities 
in the channels of exit." h. f. b. 
Lead ami Zinc Deposits of Missouri. By Arthur Winslow, assisted 
by James D. Robertson. (Missouri Geol. Survey, C. R. Keyes, State 
Geologist; vols. 6 and 7, 763 pages, 40 pis., 3 folded maps; JeffersonCity, 
1895.) As gleaned from the preface, the investigation was begun, first, 
in connection with the U. S. Geological Survey, and later independently. 
During the past year the extent of the report has more than dovibled 
over the estimate first made, probably due to the fact that since the 
authors' relief from the administrative work of the survey they have 
been able to devote all their time to the preparation of the report. 
The report has t^een divided into three parts. The first portion con- 
tains an historical sketch of the metals and a svunmary of what is known 
of them in all countries of the globe. Particular attention is given to 
the lead and zinc producing districts of North America with which the 
Missouri product is brought into competition. A chapter is also de- 
voted to the metallurgy of the metals, and the various processes are 
described with sufficient minuteness for all practical purposes. Concise 
tables of the production in the United States are also given in this con- 
nection, together with the prices. 
The second section outlines the history of mining in Missouri, and 
the general geology of the southern half of the state. The development 
of the mining in the state is traced from the time of the earliest explo- 
rations. The physical characters of the lead and zinc regions are de- 
scribed at length. The geological formations containing the metals 
vinder consideration are referred to in a general way, and considerable 
detail entered into in the case of the most important localities. The 
lithological differences are compared and some of the salient structural 
features pointed ovxt. Under ore deposits is a full consideration of the 
distribution, the form, strvicture and composition of the ore bodies, 
their manner of formation and the origin of metalliferous veins. Con- 
cerning the latter topic, the various thgkories are set forth and their ap- 
plication to Missouri "deposits clearly given. Smelting and manfacturing 
received the attention they demand, and full statistics are given regard- 
ing the production of the tvi^o metals in Missouri, the prices received 
from year to year and the total output of the various counties. 
The third part is an account of the Missouri mines, with a systematic 
and detailed description of the important developments and occurrences 
of lead and zinc. Three districts are recognized, the southeastern, the 
central and the southwestern. Here is incorporated all the detailed in- 
formation concerning the various camps. Many of these are mapped 
and the workings of typical individvial mines plotted. This is the por- 
