HLAWOoRTH. | Ore Deposits. 125 
removal by erosion could not and did not have a most marked 
influence in concentrating the unusually rich bodies of zinc 
ore and lead ore in the ore mining districts. 
By way of résumé, then, the writer would summarize his 
views regarding the origin of ore bodies in the mining dis- 
trict somewhat as follows: 
First.—The prevailing ground water throughout the min- 
ing area is surface water, probably more than ninety per cent. 
of it having fallen as rain farther west than the surface ex- 
_ posures of Silurian rocks in the Ozark area. This water has 
worked its way downward through various openings in the 
Burlington limestone, as water generally does, and has 
joined the permanent body of underground water which, 
also, is migrating slowly westward, down the inclined bed- 
ding planes of the Burlington rocks, and here and there mani- 
fests an artesian effect, as is universally the case the world 
over where such conditions obtain. Added to this ground 
water is an unknown but relatively small amount of water 
which may work its way upwards from the underlying Silurian 
rocks. ‘These waters mingle and become as one body, making 
it impracticable to separate them from each other in effect 
and in their influence. 
Second.—The fissures and openings where the ore now oc- 
curs were produced, first, partly by earth movements which 
fractured the rocks, the flints vastly more extensively than 
the limestones on account of their greater brittleness, and, sec- 
ondly, by the dissolving out of limestone interbedded with 
flint. These fissures and openings were modified and greatly 
enlarged by the stretching movements due to processes which 
uplifted the Ozark area, the forces of which acted radially, 
stretching the surface and increasing its dimensions rather 
than contracting them, as would have been done had the 
forces acted tangentially. Also, there was produced a con- 
siderable amount of local radial contraction due to the dis- 
solving of the limestone and the falling together of all residual 
material, such as flint and residual clay. This local radial 
coatraction in places may have produced small vertical dis- 
placements, the exact value of which cannot be determined, 
but sufficient to produce local fault effects, with the, faults 
