398 GEOLOGY OF OHIO. 
Among those most prominent in these explorations, Mr. A. Wil- 
helmi, of Dover, the Dover Furnace Company, and the Ridgway-Burton 
Company, of Massillon, deserve special mention. 
b. Kidney Ores. 
The kidney and block ores of the counties now under considera- 
tion remain to be briefly noticed. They are limited to the two counties, 
Stark and Tuscarawas, and almost exclusively to the latter. 
The kidney ores will be first treated. Mention has been already 
made of the occurrence of many nodules and kidneys in the shales 
above the blackband, which are often mined with the latter. These 
require no further notice, and only one horizon needs to be named as a 
further source of kidney ore in this district. The Kittanning shales, 
or the 20 to 40 feet of clay and shale that separate the Lower and 
Middle Kittanning coals, have already been shown to be a chief reposi- 
tory of kidney ore in the territory to the southeast of this. The 
“placer” mines of the Little Beaver Valley have obtained most of their 
ore from this source, as has been stated. But the same stratum proves 
even richer in ore as it is followed to the westward. At least the kid- 
neys are gathered here into a distinct seam that justifies mining on a 
small scale. 
The ore is known in Tuscarawas county as shell ore. Its place is 
immediately under the thin seam of coal that comes into the section 
locally, midway of the Kittanning shales. This leaves the ore about 
20 feet above the Lower Kittanning coal (No. 5), and about the same 
distance below the upper seam (No. 6). The ore occupies 4 or 5 feet 
of white and purplish clay, and will aggregate 12 to 18 inches in thick- 
ness. In quality it is excellent, only the mellow and aerated kidneys 
having been reached thus far in the simple style of mining followed. 
All the ore that has yet been dug, has come from the shallow benches 
cut down around the edges of the hills. It is only in the neighborhood 
of the furnaces, and along the lines of the railroads, that mining has 
been carried even as far as this. It is not known that a single drift has 
ever been carried under the hills in pursuit of the kidney ore. 
This horizon can scarcely maintain itself in present competition | 
with the blackband hills where nothing less than 2 feet of ore is counted 
mineable, and where the average of entire acres will exceed 5 feet, but 
it is well to remember that the kidney ore is here, and that its aggregate 
