614 GEOLOGY OF OHIO. 
uses in building. The prevailing color is light-gray, with yellowish and 
bluish tints intermingled. 
The bottom hackletooth, which lies just above the courses already 
named, is the bluest stone in the quarry. It is fourteen inches thick, 
and quite free from flint, and is, therefore, counted as one of the most 
desirable layers found here. The top hackletooth is thirteen inches thick, 
and is raised in blocks adapted to columns, more easily than any other 
course, and thus comes to be used for this purpose quite extensively. It 
is light colored. It is overlain, asin the previous section, by a nineteen- 
inch course, which furnishes only building stone. The sixteen-inch 
course, next above, splits very readily into the “twin eights,’ two very 
serviceable layers, which are well known and widely used. The ten- 
inch course that covers them, like the upper hackletooth, is raised in 
long blocks, and so furnishes very convenient stone for steps, to which 
purpose it goes quite largely. The “rough rock” here falls below two. 
feet, and is overlain, as in the Smith and Price quarry, by the “sheep- 
skin,’ one of the valuable, though thinner, courses of the quarries. 
The cutting stone of the quarries ends with this course. It will be ob- 
served that ten layers of stone here, deserve this name, or double the | 
number that is reported at Smith and Price’s. This is explained by the 
fact that the State quarries reach a lower horizon, a horizon which, ev- 
erywhere in Ohio, yields the heaviest courses of the formation, and, also, 
from the fact that the latter quarries have been driven further back into 
the solid rock than the former. 
An interval, varying between eleven and fourteen feet of quite thin 
layers, useful for lime manufacture, and, to some extent, as building 
stone, come in before the horizon of the bone bed is reached. This last 
division is highly fossiliferous, and contains many of the characteristic 
fossils of the formation, to which reference will again be made. The 
upper beds are softer, and occasionally particolored, and are sometimes 
styled the “calico stone.” 3 
It is probable that the heavy course taken up from the bottom of the 
State quarries, nearly or quite exhausts the descending scale of the Cor- 
niferous limestone. It has not been found possible to settle this beyond 
question, but the facts are these: North of the county line, in the val- 
ley of the Scioto, the junction of the Waterlime and Corniferous 1s seen. 
It is there found that the thick beds shown at Corbin’s Mills, and at 
Dublin, are very near the boundary of the formations. Again, in the 
valley of Big Darby Creek, below Georgesville, the contact of these two 
formations can be seen; and here, again, several massive courses mark 
the beginning of the Corniferous deposits. The boundary, at this point, is 
