24H The American Geologist. April, 1895 
cause it to rise well into the limestone rocks in the valley where 
the texture and structural conditions allow. » 
This statement includes the more important evidence which 
favors the hypothesis advanced. It is thought that it ex- 
plains existing conditions better than does any other. Of 
course, there is much more additional work needed in the 
field and in the laboratory to supplement what has been done. 
There are many detail-s of the chemistry of the processes of 
solution and deposition of these ores, the causes controlling 
the localization of deposits, etc., which need elucidation : and 
it is hoped that this report may be the means, to some extent, 
of stimulatino- such work. 
ON THE MUD AND SAND DIKES OF THE WHITE 
RIVER MIOCENE. 
By K. C. Cash. Ithaca. X. V. 
During the past few years attention has been called by va- 
rious authors to the occurrence in wideh^ separated localities 
of dikes of sandstone, which ]>ierce for many feet the neighbor- 
ing strata. The nu)St i)r()nounced occurrence of these dikes was 
reported by INIr. J. 8 .Diller from northern California (Bull. 
Geol. Soc. Am., vol i, j). 411). The article contains a full ac- 
count of tlie nature and occurrence of these dikes and the 
author's conclusion that they are intrusions of sand from 
below, along cracks determined by volcanic action (p. 437). 
In describing the dikes he says, "the dikes are nearly vertical, 
wall-like masses of sandstone, varying from a mere film to H 
feet in thickness. * * * The dikes are parallel to the 
joints in the vicinity and so related to tlu-m as to indicate 
that the joints have not been produced by the dikes, but that 
on the contrary the position of the dikes has been determined 
by the joints." 
From the occupancy of preexisting joints by the dikes and 
from the position of the mica grains in microscopic sections 
of the sandstone Mr. Diller reaches the above stated conclu- 
sion, that the dikes are intrusions from below. To account 
for this intrusion he calls attention to the fact that below a 
certain level the materials of the earth's crust are saturated 
