1 90 The American Geologist. September, issu 
CORRESPONDENCE. 
Correlation in the Ozark Region: A Correction. To the 
yovithful student one of the most fascinating phases of geological work 
is the making of correlations. While passing through this early period 
of science study, the writer fell into several radical errors of this nature, 
one of which has just come to light. As I make it a point to acknow- 
ledge and correct such early mistakes in my published statements and 
conclusions as soon after they are discovered as convenient, I have 
hereby hastened to record the correction of the error of correlation re- 
ferred to above. The making of it may be charged against youthful 
enthusiasm and inexperience. 
While residing in southern Missouri, about five years since, I studied 
out the geologic column of the stratigraphy of Stone and Barry counties 
in southwestern Missouri. About at the base of the Kinderhook group 
and apparently under the well-marked Louisiana limestone, I found a 
series of shale and limestone strata of post-Ozark age, which from my 
wrong identification of the "Green shale" as the equivalent of the Eure- 
ka shale, I described as the Devonian series of southwestern Missouri. 
I reconnoitred the country from my home in Stone county, across the 
White River basin to Eureka Springs, in Arkansas, and traced the 
prominently outcropping layers of the Louisiana limestone to that town, 
where they seemed to be separated from the Lower Magnesian or 
Ozark series by the "green shale" only, no exposures of the true, black 
Eureka shale coming within my field of observation; hence my grave 
error of correlation. 
Recently I have retraversed the territory, and have seen the real 
Eureka shale not only under the "Green shale", but under my entire so- 
called "Devonian series" except the basal conglomeratic sandstone. 
The Eureka shale is black in color, thinly laminated, and radically diff- 
erent in lithologic character from anything in the Lower Carboniferous 
strata. At Eureka Springs, I found it eight feet thick, but farther west 
in Benton county. Ark., and McDonald county, Missouri, it is reduced 
to a scarcely noticeable layer of soft, shaly material, two orthree inches 
in thickness. Wherever seen, its upper limit is sharp, there being an 
extremely sudden change from the black shale to the gray limestone. 
Under the black shale is, at Eureka Springs and throughout that 
section of northern Arkansas (as described in the Arkansas geological 
reports), a bed of sandstone generally several feet in thickness, which 
constitutes the lower member of the Devonian. It is known as the Syl- 
amore sandstone. It is this same formation, reduced to a thickness of 
two inches to one foot in the section of Stone and Barry counties, Miss- 
ouri, specially studied by me, that is the "Basal Congloineratic Sand- 
stone" of my so-called "Devonian series." 
Over the Eureka shale, at Eureka Springs, Ark., is the so-called "St. 
Joe marl:)le,"the Arkansas equivalent, in part at least, of the Louisiana 
limestone or basal member of the Kinderhook group of Missouri. This 
is commonly described as a unit, but is properly made up of four quite 
