STRATIGRAPHICAL GEOLOGY 
253 
regions were fresh in his mind. Schoolcraft ^ many years before 
had used “Metalliferous Limestone,” and Featherstonaugh ^ had 
described in some detail the “Galeniferous Limestone.” Hall’s 
proposal was clearly a third name having identically the same 
mineralological significance. 
It is sometimes taken for granted that Hall’s Galena Lime¬ 
stone derives its title from the country east of Joe Daviess County, 
Illinois, which was at that time a center of lead mining industry 
of Illinois. There is nothing in the original description to support 
this notion. J. D. Whitney, who was Hall’s chief assistant on the 
Iowa Geological Survey, plainly indicates that there was no in¬ 
timate connection between the two terms. His nearest allusion 
is the following statement: ^ “The custom house at Galena, a city 
surrounded by bluffs of the Galena, is built of rock from the Car¬ 
boniferous Limestone group.” 
As a geologic title Galena Limestone was proposed under 
misapprehension of its true stratigraphic affinities. At that time 
the lead-bearing dolomite was believed to be a distinct stratum, 
reposing normally upon the blue fossiliferous limestone. This 
notion generally prevailed until very recently, when Prof. W. H. 
Norton ® made the important observation that the real difference 
between the two alleged terranes was merely local and lithologic 
and not general and formational. 
With Norton’s clue as a basis Professors Calvin and Bain 
particularly investigated the so-called Galena-Trenton rocks of 
Dubuque County the center of the lead field. They found sev¬ 
eral distinct life-zones passing on the same level from the normal, 
well-known “Trenton” limestone through the altered “Galena” 
dolomite. This circumstance alone proved beyond peradventure, 
that the two lithologically distinct rock masses really constitutea 
one and the same terranal unit.^ Singularly enough in their tabl^ 
of formations for Dubuque County, the authors mentioned ad¬ 
here to the old conception,® placing the Galena unit above the 
3 Narrative Journal of Travels through Northwest Region of United States to 
Sources of Mississippi River, etc., in 1820, Albany, 1821. 
4 Rept. Geol. Recon. to Coteau des Prairie, 159 pp., Washington, 1836. 
5 Geology of Iowa, Vol. I, p. 290, 1858. 
6 Iowa Geol. Surv., Vol. VI, p. 146, 1897. 
7 Iowa Geol. Surv., Vol. X, p. 409, 1900. 
8 Ibid., p. 398. 
