STATE GEOLOGIST. 89 
cut so as to approximate as nearly as possible what would be obtained by 
taking out a core with the diamond drill. The resources of each horizon 
are given herewith: 
. LIMESTONES. 
Lower Silurian. —The Lower Silurian or Hudson river group con- 
sists of layers of shale and limestone interstratified. The shale varies 
from less than 1 inch in thickness to 4 feet and the limestone from a 
few inches to 14 feet. It is seldom that two layers are found, one or the 
other, without a shale parting. The shales are always silicious, with the 
silica or quartz rather fine grained, which is a desirable feature for 
Portland cement manufacture. This group of lhmestones frequently offers 
faces of 50 to 100 feet with comparatively little stripping. This is the 
largest single body of limestone in the State, which will make Portland 
cement. There will be but few localities in this formation, which will not 
furnish stone of a desirable composition, as the table of analyses will 
show. 
This formation can be found in a few ridges in Miami county, in 
Preble, Montgomery, Clark, Green, Butler, Warren, Clinton, Hamilton, 
Clermont, Highland, Brown and Adams counties. The limestone is a 
dark, blue gray to purple, highly crystalline stone. The shales are blue, 
gray, and brown. (See table I at the end of the chapter.) 
Clinton.—The Clinton horizon is the only other horizon of the older 
rock formations of the State of much commercial importance for the 
cement industry. The Clinton is found almost everywhere along the 
border of the Hudson river groups, and is nearly always overlapped by 
the next formation above, which is the Niagara. The Clinton is a 
highly crystalline rock of varied colors, and compositions, and of variable 
thickness. Sometimes there is a little shale interstratified, but as a rule 
not. The upper layers are always characterized by the abundance of 
crinoid fossils. While it is the most irregular of the lower limestone 
formations, it is readily recognized, and notwithstanding its varied com- 
position quite a number of locations furnish stone of excellent quality 
for cement manufacture, as is shown in the table of analyses. It fre- 
quently happens that the lower beds of this formation are highly 
magnesian, and it is not uncommon for it to be highly mag- 
nesian throughout. At Lumberton, Clinton county, there is 12 feet of 
stone, with less than 2 per cent. MgCO,, lying on top of 5 feet with 29.94 
per cent MgCO,. At Lynchburg, there is 14 feet 6 inches with a little 
Over I per cent. of magnesium carbonate on top of 5 feet with 12 per cent. 
of MgCO, and at Leesburg, Highland county, not many miles from the 
former location, it varies from 25 to 41 of the MgCOQ,. 
The great majority of this stone which is of proper quality is from 
7 to L5 feet thick, and so located that if more than 10 to 20 acres were to 
