The Helena independent. [volume] (Helena, Mont.) 1875-1943, 1891-06-07

In this cut "a represent the granite base;
BIB, the limestone seen in Mount Helena;
&C, clays and shale strata lmpervlous TO
water and making Il watertight bottom of
the basin: IS, strata of sandstone p%ervious
to water, into the edges of which the water
runs from the sur ounding mountains and
percolates down to the lower parts of the
valley; 90, strata of clay and clay shales
resting on the sandstone as u second water
tight basin like &C below it, both of them
continuing the water in the sandstone and
preventing it from running out into the low
pa is of the valley; w, the soil and gravels
resting on the stratified rocks in the valley;
do, horizontal line.
This cut gives the structure and position
of the rocks in the valley after the noun
tains Ground it were forced up, lifting with
them the edges of the stratified rock all
around the valley into the basin shape shown
in the cut. These stratltied rocks were the
surface rocks of a level country before the
mountains were forced up through them.
If a tin pan were taken to represent the i'm
pervious strata of clay shades, &C, and an
other pan a little smaller to represent 90,
be placed in the former with a stratum of
sand between them an inch thick, to repre-
sent the sandstones. IS, we might the better
understand the position of the rocks In this
valley. IF water be poured into the sand
between the pans, it would fill the sand up
to the top of the pans. If now n hole be
bored in the bottom of the upper pan and
a small tube be fixed water tight in the hole
so that the lower end will open into the
sand, and the upper end be a little lower
than the top of the pun, the water liz the
sand will run up through the tube and over
the top forming an artesian we'll. Such
would be the effect of boring through the
clays and shales. 90, into the sandstone,
SIS, and tubing the hole-water would rise
to the surface.
This cut does not represent all the strata
~ r,nku ~ fha yallay. INIT inst pnnuub Of
them to show how water may be forced to
the surface through a boring and form an
artesian. well.
The rocks in the Prickly Pear valley are
of the same ag6-tertiary and cretncious-
and In the same basin shape as the rocks
are in the London and Paris basins where
80 many artesian wells have been bored.
How thick these rocks are down to the
limestone no one knows. In some places in
the state they are at least $1,000 feet thick,
IA on Rocky Fork below Red Lodge, whore
they are SO tipped up their thickness can
be observed. Here they are not near sc
thick.
Thus far facts only have been stated and
no theorctic speculntions asconld be shown
were there spncs and time; and there il
only one known cause to make the obtain
ing of ~artesian wells in the Prickly Pea,
valley uncertain. The Prickly Pear has Gu
u passage through the rim OF tins basin u
elnpty its waters into the Missouri. Mheth
er this cut Is so low RS to let the waters out
| have had no opportunity to oh
, serve; but it il not probable, or tn
water so abundant in the surfac
r gravels would be drained off. Were it no
for this cut in TIE rim of tho basin the sue
cess of boring in the proper places woui
+ be assured beyond every reasonable doubt
t Perhaps an examination would remove thi
o doubt.
Even If the Prickly Pear has cut the III