252 
STRATIGRAPHICAL GEOLOGY 
These widespread occurrences of a bed of volcanic ash, or ben¬ 
tonite, in the Ordovicic strata of Tennessee and the neighboring 
states, indicate that additional discoveries along this line may be 
looked for throughout the Appalchian region of eastern United 
States. 
Nelson. 
Galena Limestone as a Terr anal Title} In the name Galena 
Limestone there lurks a last, lingering trace of Eighteenth Cen¬ 
tury nomenclature. It is, perhaps, the only instance of the kind 
which remains in this country. During a long period of more 
than two generations the title, so manifestly invalid as it appears 
to be, unscathingly runs the entire gauntlet of terminological crit¬ 
icism. How it manages to hold its own despite the vicissitudes 
of all these years is something of a mystery. Although plainly 
a Wernerian relic it appears today almost as valid a geological 
title as any of its latest geographic compeers. 
Galena Limestone does not appear, as is generally surmised, 
to be a specific place name that was at first applied to a special 
rock formation. Strictly speaking the term does not refer to a 
definitely defined terrane at all. As originally proposed the des¬ 
ignation really covers merely an irregular, mineral-bearing portion 
of a regular stratigraphic unit. Only recently is the title extended 
to a terranal sense. 
When the term Galena Limestone was first suggested by James 
Hall,^ so long ago as 1858, it was intended to particularize the 
dolomitic, lead-bearing body of what had been previously known 
as the Upper Magnesian rock. Thus, at the time when the title 
Galena was first used geologically, it alluded strictly to the ore- 
content of the formation. Although at this period he had already 
begun the practice of proposing geographic names for geological 
terranes in New York state Hall had not yet entirely emancipated 
himself from Old World influences of his youth, or of his We- 
nerian teachers and contemporaries in the East. 
Of the twenty-five terranal titles which Hall used in his Iowa 
reports fully one-third of this number are old mineralogical 
names. Moreover, the rock terms in common usage in the mining 
1 Published without permission of the State Geologist. 
2 Geology of Iowa, Vol. I, p. 60, 1858. 
