History of Saginaw county, Michigan; together with ... portraits ... and biographies ... History of Michigan ...

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HISTORY OF SAGINAW COUNTY.
11

the casing should be set so firmly in the rock as to prevent any
sand or gravel from running in under the tube, and thus getting in
on top of the drill and endangering its becoming fastened in the
well.
"The rock-drilling now commences and continues to the depth to
which it is proposed to sink the well. After the drilling is done,
the sides of the well are smoothed off with a tool called a reamer.
In most of the salt wells on the Saginaw river an offset is placed
in the well at a short distance above the lower sand rock. Below
the offset the size of the well is lessened half an inch in diameter.
On this offset is made the so-called rock-packing, the hole being
drilled beveling so as to receive a tightly-fitting iron collar or
funnel-shaped piece of metal. A tube corresponding to the size of
the upper part of the well is made to rest on this rock-packing as
the offset, and runs to the top of the well; in this way all the weak
brine from the upper rock and any fresh water that may come into
the well above the offset are shut off. Below the offset the tube
continues in reduced size to the locality of the lower sand rock, at
which point the pumping chamber containing the pumping valves
is placed.
"In the early history of salt well boring in Michigan, the pressure
of the brine in the well tube forced it within 100 feet of the surface.
More recently, owing no doubt to the great demand for brine, it
does not rise so high. It only requires a small amount of power,
after the pumping rods are properly balanced, to lift the brine out
of the well into the settling tanks.
PUMPING BRINE.
"Often in starting up a new salt well the brine is weak, that is,
shows a small percentage of salt by the salinometer. This arises
from the fact that a large quantity of fresh water or weak brine
from the upper formatiuns has passed down into the well during
the time the well was opened or being tubed. To test this point,
and to bring the brine up to the usual strength of salt brines, the
pump is put in operation and run for some time. If the brine continues to show an increase of strength on being tested by the
salinometer, the pumping is continued until the strength of brine
remains permanent at such a percentage as wells of equal depth in
the same locality have shown. If, however, the brine does not
increase in strength, there are strong probabilities that there is a
leakage of fresh water or weak brine into the well at the offset.
This should be remedied at once-the more so if the well is a deep
one, such as most of those in tlhe Saginaw Valley are; for in this
case the offset in the well is below the so-called gypsum formation,
and you are drawing in and mixing with your strong brine a weak
brine from these formations which has a higher percentage of
gypsu in.
"'This mixing of the two brines in thle well and tubing causes a
precipitation or separation of the gypsum upon the pumping rods