342 The American Geologist. June, isgo 
In October, 1889, Mr. C. H. Gordon published'^ an article on 
the geology of southeastern Iowa in which he gives the records 
of some deep wells bored at Keokuk, Ottumwa and Sigourney. 
At the former and the latter places the Maquoketa shales were 
recognized. Keokuk is in the extreme southeast corner of the 
state, and is about 60 miles south of Washington. Here the 
shales are recorded as being 63 feet thick and 800 feet below 
the surface. Sigourney is some 25 miles west of Washington 
and here the shales were 140 feet thick and 1030 feet below the 
surface. Not allowing for the drift, the shales at Washington 
are 702 feet below the surface and 91 feet thick ; at Sigourney 
they are 1030 feet below the surface and 140 feet thick ; while 
at Keokuk they are 800 feet below the surface and only 63 feet 
thick.2° 
In 1889 Mr. E. 0. Ulrich published-' some notes upon old 
and descriptions of new species of corals, polyzoa, and ostra- 
cods from Stony mountain, already alluded to. Mr. Ulrich 
calls the rocks "Hudson River or Cincinnati" and in a sum- 
mary enumerates twenty-n^ne species of fossils. Of these no 
less than twenty are also found in the Cincinnati group of Ohio, 
Indiana and Illinois. 
While the references here given comprise all that have been 
noticed as dealing with the Maquoketa shales, or rocks which 
have been referred to this formation, it should be remarked 
that Dr. John Locke in 1839 described" the strata and figured 
a section from the Little Maquoketa River, some seven or eight 
miles west of Dubuque, eastward to Sinsinewa mound in Ill- 
inois. Dr. Locke, however, referred the rocks to a horizon 
which he regarded as the equivalent of the "Cliff limestone" of 
Ohio, now known as the Niagara, and placed the lead bearing 
Galena limestone with the Lower Magnesian of Dr. OAven. He 
did not recognize the existence of the shales as separating his 
Magnesian from the Cliff limestone above. 
"American Geologist, vol. 4, pp. 237-239. 
^°The great thickness of the drift at Washington, 350 feet, is certainly 
abnormal, and the well was probably located in a river valley. Con- 
siderable discrepancy in the depth of the shales beneath the surface 
and in their thickness, is shown in these well borings. 
^'Contri. to Micro-Palfeon. of the Cambro-Silurian rocks of Canada. 
Part 2. Geol. and Nat. Hist. Survey of Canada, Montreal, 1889, pp. 27- 
57. 
"Owen's Survey of Iowa, Wisconsin and Illinois in 1839. Eeprint 
edition of 1844, pp. 152, 153. 
