126 GEOLOGY OF OHIO. 
Different conditions of growth and accumulation are indicated by 
such facts, and glimpses are afforded in them of the physical geography 
of these distant periods. 
The connections, which it has been the object of this alapees to 
establish, have been made to rest us little as possible upon assertion. 
The ability to recognize the several Coal Measure limestones, the Mer- 
cers, the Putnam Hill, the Ferriferous, the Freeports, the Cambridge, 
and the Ames, is of course involved in the construction of sections in 
which these elements occur, but they are so well characterized as a rule 
that it is not asking very much that this ability shall be conceded. 
The identifications made by others, and continuity that is based on gen- 
eral knowledge, have been brought into requisition in very many 
instances. Even the measurements of other geologists have been fre- 
quently adopted in order that the conclusions may be seen to rest as far 
as possible on the consenting and harmonious testimony of many, rather 
than on the judgment of one. 
The illustrative sections might have been multiplied indefinitely, 
but it is believed that enough have been given to weld the series of the 
several fields. It is not denied that in the establishment of this unity 
of history, such sections as would best illustrate it have been selected, 
but in all cases the range of measurement and variation has been stated 
for the several subdivisions of the field. 
The uncertainty in which some questions of identification have 
been left is not the result of unusual obscurity in the subjects them- 
selves, but rather of the necessary haste with which the work of ex- 
ploration has been conducted. There are but few insoluble problems, 
to say the least, of a stratigraphical character in the Lower Coal Meas- 
ures of Ohio. | 
The results of the investigations that have here been recorded may 
be thus expressed. There are in the Lower Coal Measures of Ohio, or 
in other words, below the lowermost division of the Mahoning sand- 
stone, twelve regular seams of coal, all of which are of mineable thick- 
ness (24 inches and over) in some part of their extent. In this enumer- 
ation, the Lower Clarion and Upper Clarion (Scrub Grass) are counted 
as distinct seams. Furthermore, there are two seams that are found 
in a great many sections, the No. 5a of Newberry from the Tunnel 
section at Mineral Point, and the 18-inch seam so often found between 
he Middle Kittanning and the Lower Freeport coals in Columbiana 
