Haworts. | Detailed Geology. 91 
to prospect. Invariably the prospector wishes to operate 
along the sunken ravines and valleys which to a degree seem 
to have been produced by a settling or subsiding of the 
surface. This is true to so great an extent that the writer 
on different occasions has had his attention called to it in 
other parts of the state. The valley of a small creek or 
stream similar to valleys in the mining district just described 
has been pointed out in different places throughout Missouri 
and Kansas, with a statement that Mr. So-and-so, a ‘“‘ prac- 
tical Joplin miner,’’ advised prospecting for lead and zinc ore 
here on account of the lay of the ground. 
Origin of Fractures. 
Fractures described in previous pages have had an origin 
subsequent to the solidification of the flint and previous to 
accumulation of the ores and secondary flint. It seems 
probable that they originated in connection with earth move- 
ments which produced the Ozark dome, although some may 
be much older. The general result produced by such move- 
ments was the uplifting of an elliptical area, producing a 
structure approaching the monoclinal type so common in 
America. That is to say, the process produced a stretching 
of the surface rather than a contraction. This is shown in 
many places. ‘The wide fissures now filled with Coal Meas- 
ure shales are evidence of it, as are also the various ‘‘ horse- 
backs’’ in coal fields near by to the northwest. This 
stretching, or surface increase, with the consequent periph- 
eral tension faults, was described by the writer® in connec- 
tion with a discussion on the geological position of ore bodies 
surrounding the Ozark dome. Adams®* apparently mis- 
understands this reference, as he objected to it on the ground 
that there was no evidence of an intrusion of sufficiently 
large masses of molten material to produce the elevation, and 
this in the face of the fact that the entire paper was written 
mainly to show that the ore bodies of the Ozark area origi- 
nated independently of heat phenomena! 
Flint is so brittle that under most circumstances it has 
fractures produced in it without any apparent fracture of ad- 
31. Haworth, Prof. Erasmus: Bull. Geol. Soc. Amer., vol. XI, pp. 231-240. 
32. Adams, Dr. George I.: 22d An. Rep. Director U. S. Geol. Surv., part II, p. 93. 
