FOWKE] ABORIGINAL FLINT QUARRIES 507 
and cracked, easily shattered, breaking in any direction, and soon 
falling into fragments when the inclosing rock is dissolved. Owing 
to these defects, it was not adapted to the needs of those who were 
compelled to use stone implements, though occasionally a piece of it 
might be found which under stress of necessity could be converted 
into a serviceable tool or weapon. 
Ascending the geological scale, no more chert is found until the 
rocks of the middle Carboniferous or “ Coal Measures” are reached; 
the strata lying in the upper divisions of the Mississippian and 
lower portions of the Pennsylvanian, to designate them according to 
modern geological nomenclature. Here conditions seem to have been 
especially favorable to the formation of chert; including in that term 
the varieties classified as “silica”; flinty limestone (a mechanical mix- 
ture of lime and silica) ; buhrstone; flint; jasper; hornstone ; basanite, 
or lydite, either glossy or dull; novaculite; chalcedony ; or, in banded 
or mingled coloration of the last, as “agate.” “Silica ” is a common 
name applied to a stratified rock, each layer being practically uni- 
form in thickness, though some beds are heavier than others. As 
it resembles ordinary limestone deposits in depth and extent, it is 
supposed to be not always an original formation, but to be due largely 
if not entirely to a process of substitution or replacement, limestone 
being dissolved and carried away by percolating water which leaves 
silica in its place. Chalcedony and novaculite are usually formed 
under open air by evaporation of water from springs, though the 
latter is sometimes a precipitate. Agate and allied stone is similarly 
formed, in crevices and cavities of massive rock. Such of these mate- 
rials as can be readily converted by aboriginal methods into imple- 
ments or weapons are grouped in popular parlance under the generic 
term of “flint.” They are found principally in one geological hori- 
zon, which in the earlier Ohio surveys is called the “ Hanging Rock 
limestone,” from its marked development in the vicinity of that town, 
formerly an important iron-manutacturing town in Lawrence County 
on the Ohio River. The equivalent of this formation, bearing vari- 
ous names according to locality, occurs in southeastern Ohio and 
adjacent parts of West Virginia, reaches across eastern Kentucky 
and Tennessee, into northern Alabama, and then, on the western 
flank of the great central limestone and shale region determined by 
the “Cincinnati uplift,” passes across western Tennessee and Ken- 
tucky into southwestern Indiana, southern Illinois, and finally, cross- 
ing southern Missouri and northern Arkansas, extends into Kansas 
and Oklahoma. This is the vast “flint area,” where siliceous stone 
under one or another of the names listed above is found in abundance. 
Tt is not continuous, nor does any one deposit extend unbroken over 
an area more than 15 or 20 miles across. The conditions necessary 
